Cinderhulk in the Jungle - 5.8
I was messing around in the jungle in a solo custom game, trying out new builds and such with champions and using Cinderhulk. I discovered that the Crimson Raptor doesn't drop below 1 HP just by Cinderhulk's damage itself. I stood next to it for nearly a minute for the damage to kill it, and it did nothing.
It's not a massive game breaking bug, but when I ace the enemy team and we could totally get a turret, only to decide to get a Raptor camp first, I wont be able to afk and let Cinderhulk get the last hit.