Overwatch's Reinhardt is your classic tank: He's got a giant-ass shield and a giant-ass hammer, and he can be the bane of any well-formed strategy when he's in the right place at the right time. But looking at him, you might think that all Reinhardt is good for is taking bullets for his team—and that's not the case at all. His Charge ability can pin enemies and close distances alarmingly quick, and his Fire Strike gives him a much-needed ranged attack for swatting down pesky flies like Widowmaker. If you like being the center of attention, Reinhardt will make sure you survive the spotlight.
Rocket Hammer [LMB] - Reinhardt is one of the few melee-only characters in Overwatch, which isn't that much of a disadvantage when you realize how punishing a hammer to the face can be. There's a good deal of reach with this weapon, and it will also damage any number of heroes caught within its swipe while pushing them back. The only downside is, being so bulky, Reinhardt can only swing it about once per second.
Barrier Field [RMB] - The bread to Reinhardt's hammer-butter, Barrier Field is a regenerating energy shield that Reinhardt can use to absorb all kinds of incoming damage while still allowing teammate's attacks to pass through it. While using it, Reinhardt will move quite slowly and won't be able to attack. He also will become a big target for anyone who can flank him, which can be worrying when you're torn between which side you should be blocking damage from. The shield only regenerates when Reinhardt isn't using it, so be careful to only deploy it when it's needed most.
Fire Strike [E] - Reinhardt's only ranged ability is actually a pretty effective one when used well. Firestrike causes a lance of flame of erupt from his hammer and is capable of hitting multiple enemies at once. Use it to attack pesky, out of range heroes like Widowmaker or Hanzo if you're getting tired of their harassment.
Charge [LSHIFT] - The famous last words of many have been "Reinhardt is too far away to be a threat." That's when he charges forward and pins them to a wall for an insta-kill. Charge can be used purely for its mobility, but it's always best to see if you can pin a hero along the way and ram them into something. You'd be surprised how many players never see this one coming.
Earthshatter [Q] - Reinhardt's ultimate isn't the devastating finisher that other heroes have, but when used with a bit of coordination it can be the catalyst to an entire team wipe. Earthshatter causes Reinhardt to strike the ground with his hammer, knocking over and stunning any heroes within an area in front of him.
Reinhardt Strategy Tips
Reinhardt's shield is his greatest asset and learning to use it to cover your allies while maintaining its regenerating health points is crucial to being a good Reinhardt. With this shield, there's a ton of synergy with other heroes, most infamously being Bastion when he's in Configuration: Sentry mode. If your team is on defense or waiting for the attacking team to push from their respawn at the beginning of a match, shielding a well-positioned Bastion can eviscerate an entire enemy team in the opening seconds.
Reinhardt requires a good deal of positional awareness to make his shield effective, and he should always be on the front line pushing forward with it. When the shield is running low or the enemy team has dug in for a fight, use charge to rush forward and pin a weak target against a wall for an insta-kill. Once Reinhardt is in close his high health points and hammer can devastate a group of squishy heroes. If a Widowmaker, Hanzo, or Bastion sets up to hit you from a distance, throw a Fire Strike their way to make them rethink that strategy.
Because Reinhardt's shield prevents him from attacking, you'd be surprised how safe enemies will feel standing just meters in front of you while they try to break your shield. If enough of them congregate, it's time to drop your Earthshatter so your own team can quickly mop them up.
Above all else, put yourself in the center of every conflict and take as much damage as you can. Taking damage charges your ultimate and his high health means it's going to take quite a concerted effort to bring him down.