The new server browser in PTR seems very exciting. You can mess around with a lot of settings for each individual hero. People have made gimmick modes like 6v1 with the 1 "boss" player having crazy bonuses and cooldowns.
The best mode I have found so far is Mayhem/Hell/whatever you wanna call it. max movement speed, ult generation, projectile speed, zero cooldown. it's absolute madness. pharah is an orbital cannon hovering above everyone else, tracers blinking around like they had too much coffee, constant dragons crossing the map, junkrat is just flying, too, which is basically a rhythm game for the junkrat player, reinhardt flailing around his hammer is basically an aoe attack, and so on, and so forth...