Some Overwatch myths have been verified.
Two Lucios will not heal you faster than one, but two Mercys will.
Reinhardt can pin D.Va's mech while it's self-destructing, moving it away from teammates. How selfless!
If you put one of Torbjorn's turrets over a health pack, it will use it to heal.
Reinhardt's charge can be stopped short by one of Junkrat's traps.
D.Va can block Hanzo's ultimate if she blocks the arrow with her shield before it turns into its Dragonstrike form.
D.Va can kill an opponent by calling in her mech while next to them.
Nice! Little tips and tricks like that can add up. I'll add a few I've come across that may not be super obvious.
D.Va calling her mech won't kill them outright, just does damage (probably what you meant, just wanted to clarify it's not a one-shot. think it does maybe 50 damage?).
McCree's flash stun can stop Reinhardt's charge.
Genji can reflect Hanzo's ult if he reflects the arrow before it turns into its Dragonstrike form.
D.Va's shield can block and completely cancel Zarya's ult if the projectile hits the shield before hitting the ground.
Pharah can use her concussive shot to move herself quickly (blast the ground or when you're next to a wall).
Pharah's concussive shot supposedly (unconfirmed by me anyway) does damage to shield HP (the blue hp blocks that Zarya has and Symmetra can put on peeps).
Hanzo's sonic arrow (that reveals people) can actually be shot into players (I didn't know that. haha). It does the same damage as a regular arrow. Characters that can shake debuffs (Tracer, Reaper) can drop the sonic arrow so it no longer reveals them or nearby allies. Only if they are specifically hit with that arrow.