Some heroes can skip their reload animation by meleeing in the middle of it. Most notable on Reaper - it reduces the 1.5 second reload to like .75 seconds. Everyone else has to melee in the middle of the animation, so it's not quite as noticeable but still is an advantage.
Appears I was wrong.
McCree was only nerfed if you're bad with accuracy. Flash bang + double headshot is still 305 damage. It's just not as easy as right clicking.
Hanzo's E can 1shot more than half of the heroes in the game - Aim at their feat, specifically the center of their model between their feet for most heroes.
Junkrat's Concussion mine does quite a bit of damage - don't be afraid to use it offensively.
Pharah's Rockets can be used to give you a boost or make you move away from a wall very quickly. Useful for pharah vs pharah - your rocket only does 35 damage to yourself. Better than eating a direct missile!
Damage is VERY noticeable and may make people react instantly - even if it's a long range 1 damage tracer shot. I've saved quite a few healers by just shooting reaper from long range with low damage, making him wraith form.