Symmetra:  Winston is the best counter to Symmetra's Sentry Turrets.  All Winston has to do is walk in the room filled with Sentry Turrets and hold down the trigger for his Telsa Cannon, it will automatically aim and kill each one quickly.

Symmetra on the other hand can fire her Photon Orbs and her Photon Projector inside of Winston's Barrier Projector, making your barriers completely useless against her.

Winston has the capability to leap right up close to Symmetra, throw down a barrier and then take her out quite easily as she has no escape mechanisms at her disposal.  Winston is also decent at hunting down Symmetra's Teleporter ultimate thanks to his frequent Jump Pack leaps.

Hanzo:  Winston's Barrier Projector does a good job of protecting his team from Hanzo's Storm Bow shots.  Leaping at Hanzo is very effective since he can't do much in close range, except fire a Scatter Arrow shot at you or attempt to escape by climbing a wall.  Up close and Winston's Tesla Cannon, Barrier, and Primal Rage are very deadly to Hanzo and his relatively weak hitpoints.

If there is a lot of allies inside of Winston's Barrier, Hanzo can fire a Dragonstrike at it to force you and your allies to scatter out of the barrier.

Genji:  Genji's Deflect ability has no use against Winston and his Tesla Cannon.  Winston's Barrier further protects him and his allies from Genji's shurikens.

If Genji happens to get close and use a Swift Strike (which does 50 damage), it simply won't be enough to put a dent in Winston's large 500 00 hitpoint pool.  Plus Winston's Tesla Cannon will automatically keep aiming at Genji while he does his Swift Strikes.  If Genji tries to run away, Winston can simply leap after him to take him out.

The only thing to really watch out for is Genji's ultimate Dragonblade, as it will deal more DPS than you can do back to him and your barriers will have no use against it.  Consider leaping away from him to avoid his Dragonblade damage.

Widowmaker:  Winston's Barrier shields are powerful against Widowmaker for blocking all her shots temporarily protecting him and his team.  Winston can use his Jump Pack to leap right to Widowmaker and deal damage with his close range Tesla Cannon or turn on his ultimate Primal Rage to knock her around.  However, if Widowmaker survives any immediate damage she can counter that by grappling away from him.  Winston's high HP means it will take a lot of good shots from Widowmaker in order to take him down.

Mercy:  Winston happens to be decent at flanking enemies with his Leap/Barrier combo and it works especially well against Mercy.  Mercy is also a prime target to flank as her heal and resurrect abilities are very powerful and you will want to make sure she is disabled from combat as much as possible.

If Mercy is heavily guarded then you will need to wait until Primal Rage is ready before leaping at her.

Torbjorn:  Once again, Winston can do his Leap/Barrier combo against Torbjorn and his turret, and if timed correctly Winston can put the Barrier down right in front of the turret so the turret will hit the barrier instead of Winston, then he can deal damage to the turret with his Tesla Cannon while his barrier absorbs the damage from the turret.  Winston can then use his ultimate Primal Rage to clean up Torbjorn and any other enemies in the area. 

After leaping towards Torbjorn and his turret, you will need to watch out for Torbjorn using his ultimate Molten Core.  If Torbjorn is repairing his turret with Molten Core, try to take cover from the turret with a Barrier shield and dish out damage to Torbjorn.  If Torbjorn attacks you then attack whichever is lower in health between Torbjorn and the turret instead.  If Primal Rage is available, just use that to take control of the situation.

Other than that powerful combo, Barrier Shields in general will protect Winston's team from turret damage allowing his team to push forward and take out the turret more easily.

Tracer:  Like Symmetra's weapon, Winston's Tesla Cannon works very well on Tracer thanks to the automatic aiming, as it does okay at damaging Tracer even while she is blinking as long as she is in range of him.  Because of Winston's Tesla Cannon and high HP of 500, Tracer is better off ignoring Winston most of the time and focus on weaker heroes to harass and pick off.

Tracer's Pulse Bomb is a good counter to Winston's Barrier Projector.  Tracer can blink into the Barrier real quick, lob a Pulse Bomb, then Recall out of there, dealing massive damage for anyone taking cover under the Barrier.  If Tracer throws her Pulse Bomb on Winston, his Jump Pack does NOT unstick a bomb.  However at full health, he can take a full hit from a Pulse Bomb and live it.  Winston can also activate Primal Rage to give him a 1000 HP to survive a Pulse Bomb.

If Winston uses his ultimate (Primal Rage), Tracer can simply blink away from it.

Ana:  Winston is fairly strong against Ana due to his ability to block Ana's Biotic Rifle shots, Sleep Darts and Biotic Grenades with his Barrier Projector.  This can help protect his allies against all of her attacks and can increase your allies healing potential by blocking Ana's Biotic Grenades.

Winston also excels at flanking Ana quickly by leaping up close and taking her on with his Tesla Cannon.  A well aimed Sleep Dart is Ana's best hope at surviving Winston's wild close up leaps.  If Ana's Sleep Darts are on a cooldown or if she misses her shot at Winston, she can also throw down a Biotic Grenade to do some damage to him while healing her up a bit, but she will have to hope her allies are there to help fend Winston off because Ana's poor mobility and damage output will make it hard to run away from Winston.

Ana's ultimate Nano Boost can be used on one of her allies to help improve her chances of surviving Winston's Primal Rage by providing possible cannon fodder for Winston to bat around instead of Ana.  Ana can also Nano Boost one of her allies to help deal with Winston's wild Leap flanks.

Winston's ultimate Primal Rage can be annoying to deal with for Ana, as long as Ana keeps her distance from him she should be okay.  Even though Primal Rage has a big hitbox it can still be tough for Ana to aim Sleep Darts at him during this time.  Even if she does land a Sleep Dart on him, Primal Rage is one of the few ultimates that will continue if it gets awakened while sleeping.

McCree:  Winston can block McCree's shots with his barrier shield, protecting his team at the same time.  Winston's Jump Pack helps him to stay away from McCree and his Flashbangs.  Since Winston can only do damage in close range with his Tesla Cannon or his ultimate Primal Rage.  He is very vulnerable close up to McCree's deadly Flashbang and fan fire combo.  If Winston uses Primal Rage, McCree can still Flashbang and fan fire at him, and McCree can back away from it using Combat Rolls.

McCree's ultimate Deadeye is less effective on Winston due to his large hitpoints (of 500) and his ability to block it and protect his team with his Barrier Projector.  Plus with Winston's Primal Rage, he can leap right up to McCree using Deadeye and knock him out of view from firing his shots off.

Overall McCree still has the upperhand thanks to his strong medium range fire and up close Flashbang and fan fire combo against Winston.

Pharah:  Winston is not much of a threat to Pharah since she flies and hovers in the air most of the time and is mostly in the clear from Winston's Tesla Cannon and Primal Rage.  If you do leap at her to attempt to do some damage she can use a Concussive Blast to knock you back away from her.

However, Winston's barrier shield does a decent job at protecting his team from incoming rockets, but only temporarily.

Pharah's ultimate Barrage is not very effective against Winston since he can just use a Barrier shield to block it and protect his team or leap out of the way from it.

Reaper:  Reaper's shotguns are very deadly, as it can only take 4 close up shotgun shots to take out Winston.  You will find that Reaper will be harassing you more so than any other hero.  Reaper can Shadow Step behind you and then move inside your Barrier and start attacking you, or worse he can use his ultimate Death Blossom to quickly take you out.

As Winston, do your best and keep your distance from Reaper.  Leap away from him immediately if he comes close to you, stick with your teammates so they have your back, and use Primal Rage to save yourself from him if you need to.  Unfortunately, Reaper can avoid your Primal Rage by simply using Wraith Form to escape.

Lucio:  Lucio has multiple ways to stay away from Winston's close up attacks.  Lucio can use his speed aura to move away from Winston while still being able to fire his sonic projectiles at him.  However, Winston's Barrier Projectors do a great job at blocking Lucio's sonic projectiles.  Up close and Lucio can use his Soundwave ability to knock you back, which can make it hard to damage him with either your Tesla Cannon or Primal Rage.

Lucio can also use his ultimate Sound Barrier to save him and his whole team from Primal Rage, which is one of the hardest counters to it.

If Lucio uses Sound Barrier, it's best to not worry about playing offensively, but instead play defensively for the time being by protecting your team with Barriers until it's over.

Zenyatta:  Zenyatta's Orb of Discord can be tough to deal with as it will do +30% more damage to whoever has it on them.  If Zenyatta puts his Orb of Discord on Winston I recommend playing him a bit differently.  If you get the Orb of Discord, I recommend staying back with your team and protecting them with Barrier Projectors.  Discord Orb cannot be thrown through Winston's Barrier Projector.  Avoid leaping at the enemy unless you feel like you have a clear chance at leaping at Zenyatta to take him out.  If you take Zenyatta out, you will drop the Orb of Discord.  However, Zenyatta can save himself from all attacks by using his ultimate Transcendence.  So it's best to leap at him right after he uses Transcendence so he can't use it on you.

Winston also has various ways to counter Zenyatta's Discord Orb.  Winston can use his Jump Pack to quickly leap out of the line of sight from Zenyatta to drop the orb.  He can use his Barrier Projector to block damage that could be done to him.  Winston can also use his ultimate Primal Rage to fully heal him at 1000 HP which can waste the Discord Orb's potential.

Mei:  Winston's Tesla Cannon weapon only does damage in close range, so he would need to get close to Mei to do any damage to her, but Mei's freeze blaster is simply stronger.  Even if Winston uses his ultimate Primal Rage melee attacks on Mei, she can still freeze him or she can simply use Cryo-Freeze to escape it.  Mei's Ice Walls can further keep Primal Rage away from her and her allies.

Winston is better off staying away from Mei and focus on other heroes to kill.  Winston's Barrier Projectors are still effective at blocking Mei's Endothermic Blaster's frost stream and long range Icicle shots.  Winston can also escape from Mei's freeze gun by simply Leaping away from it.

If Mei uses her ultimate Blizzard, you can simply escape out of it with a leap.  Barriers won't do anything against a Blizzard.

Reinhardt:  Winston can quickly leap up towards Reinhardt and has the ability to be very deadly up close to him.  Winston's Tesla Cannon can fire through Reinhardt's shield, potentially forcing Reinhardt to drop his shield to do melee attacks or an Earthshatter to save himself unless his team can provide enough fire power behind Reinhardt.

Winston's Barrier Projectors have no use against Reinhardt as all his abilities can go through Winston's barrier, including Fire Strikes and Charge.

Primal Rage can be very deadly to Reinhardt because you can knock him and his powerful shield away from his allies, however, he can still Charge and pin you while Primal Rage is active, or worse he can use his ultimate Earthshatter to drop you down, and can follow that up with melee strikes or a Charge.

Be cautious about Reinhardt charging at you, if he does, quickly leap upwards somewhere to avoid it.

Zarya:  A good Zarya player will be able to protect any one of her allies that Winston leaps to with her Projected Barrier.  If you see these Projected Particle Barriers, don't shoot at them or your shots will simply get absorbed and will increase the damage output of Zarya's weapon.  She can also use these Particle Barriers on herself to do the same thing.  This makes leaping at defenses and other enemies a tough task.  Only consider leaping once you know these Particle Barriers are on a cooldown.

Close up battles with Zarya can be very deadly to Winston since her Particle Cannon weapon is simply more powerful than Winston's Tesla Cannon, especially when it's charged up.  Plus she can use a Particle Barrier to protect herself.  Not to mention, she is a tank herself with 400 HP (200 of it is a regenerating shield).  Zarya's Particle Cannon at 0% charge without a Particle Barrier will out beat Winston's Tesla Cannon in a 1vs1 fight.

Luckily, Winston's Barrier does block both of Zarya's Particle Cannon attacks (both her short range beam and medium range explosive charges).

Zarya's ultimate Graviton Surge is somewhat deadly to Winston since he has no way to escape it (his Jump Pack wont let him escape it), but Winston can put down a Barrier to block shots from hitting him and his allies stuck in the surge.  Zarya's Graviton Surge becomes especially deadly when she traps you into it while Primal Rage is active, making Primal Rage totally useless then.  It is possible to leap away right when Zarya tosses out her Graviton Surge, one must be very quick with the trigger on that though.

If you hit Zarya's Particle Barrier with Primal Rage it will still knock the target around but it will absorb the damage for Zarya's Particle Cannon.

Bastion:  Overall a Bastion Sentry can deal with Winston very easily.  Although, Winston can counter a Bastion Sentry thanks to his Leap/Barrier combo.  I would only do this as a flank maneuver, because if Bastion sees you coming you will most likely die to him.  After leaping towards Bastion, quickly get out of his field of view so he cannot attack you.  You might be able to take Bastion out as long as his teammates don't zerg you down or he focus fires on you precisely.  Just hold down the trigger once you get close to him while strafing and jumping around him to make it harder for him to aim at you.

If Bastion is heavily guarded, I would not bother leaping towards him.  Winston's Barrier is only somewhat effective against Bastion.  A Bastion Sentry can melt Winston's Barrier in 1.5 seconds and Primal Rage is very weak against a Bastion Sentry as it will not knock him around.

If you see Bastion use his Tank Form ultimate, you can simply Leap away from it to avoid the cannon ball hits or use Primal Rage to knock Tank Form away from your team.

Soldier 76:  Barrier Projectors will be your best friend against Soldier 76's Pulse Rifle and Helix Rockets.  However, the periods of time when your Barriers are down is when Winston can dish out a lot of damage to Winston.  Since Winston has a large hitbox, Soldier 76 will be able to do a lot of damage to Winston even from long ranges.

When you use Primal Rage around a Soldier 76, he may attempt to Sprint away from you.  But remember, your Jump Pack changes to a 2 second cooldown, giving you plenty of mobility to leap after him to take him out.

If you see Soldier 76 use Tactical Visor, rally your teammates to you and protect them with a Barrier Projector.

Winston:  Ape Vs Ape?  There's not a whole lot to say here, except that all of Winston's attacks can go through shields and barriers (except Zarya's shield), so you can fire your Tesla Cannon through another Winston's Barrier Projector.  The fight really comes down to who has the better healer on them and who can effectively use Jump Packs to retreat to health packs from a losing battle or leaping away from another Primal Rage Winston.

Roadhog:  Winston's Barrier Projector protects his team from Roadhog's Scrap Gun shots and also blocks Chain Hooks as well.  When Winston's Barrier goes down is when Roadhog can make his moves.

If Roadhog Chain Hooks you into him, you can counter that by using a Leap or Primal Rage.  However, Roadhog's ultimate Whole Hog can be used to knock Primal Rage back away from Roadhog and his team.  But you can just keep leaping to make up for that.  If Primal Rage is not available, you will need to leap away from him (and/or throw down a barrier) or he will be able to do a lot of damage to you close up.

Keep in mind that a Jump Pack landing will NOT cancel out Roadhog's Take a Breather ability (his self heal).

If Roadhog uses Whole Hog, Winston's Barriers are an excellent counter to it.

Junkrat:  Winston can block Junkrat's grenade spam with his Barrier Projector shield, protecting his team, only temporarily though.  Junkrat's Traps/Mines can be dealt with by either leaping over them or simply walking up to them and hold down your Tesla Cannon to easily take them out.  Keep in mind that your Barrier Field will block everything Junkrat has, including:  mines, traps and frag grenades.

If Winston gets close to Junkrat he can use his ultimate Primal Rage on him.  But, Junkrat can quickly throw down a trap and then mine jump away from you.  But since Jump Pack turns into a 2 second cooldown with Primal Rage, you can just leap right after him.

Junkrat's ultimate Rip-Tire can be blocked by a barrier shield, but the tire can be steered right inside of a barrier and then be detonated.  Winston doesn't have a long range weapon to shoot it with, although Winston can just leap away from it (if it's not on a cooldown).  Winston can also counter a Rip-Tire with Primal Rage to take the hit from it, otherwise one Rip-Tire will be able to knock regular Winston out at full normal HP.

Be careful after killing Junkrat close up, as his Total Mayhem death bombs do a lot of damage over Junkrat's corpse!

D.va:  D.va can be a pain to deal with, mostly because of her Fusion Cannons out DPS Winston's Tesla Cannon up close and she can also do good damage at medium range as well.  D.va is also a tank with the same amount of HP as Winston, but more since she will pop out of her mech when it gets destroyed.  This makes leaping at her a risky endeavor.  I would only consider leaping at her if her health is nearly low.  Luckily though, Winston's Tesla Cannon can go through and bypass D.va's Defense Matrix ability.

Both Winston and D.va have great mobility, since D.va can use her Boosters to fly up to you or escape from you, just like Winston can do the same to her.

If you manage to take out D.va's mech, Winston has the easiest time dealing with the little D.va that pops out, as his Tesla cannon combined with leaps will be able to easily keep up with her to take her out with no problems.

Primal Rage can be effective against D.va.  Knocking her around will still allow her to shoot her Cannons, but it can knock her away from more fragile allies.

D.va's ultimate Self-Destruct can easily be avoided by leaping away from it and hiding behind a wall.  Alternatively, a Barrier Projector can also save you and potential allies from the explosion as well, while also providing cover to continue attacking underneath the Barrier.