Fear should become Fiddlesticks' passive, because scarecrows are scarey as hell.
Garen should instantly win the game anytime he uses Judgement, because spin to win.
Jarvan's ult should last for the rest of the game, because you can't simply undo a huge impact like that.
When Lulu ults someone, Cho'gath's ult should be able to instantly kill them because I'm sure he can eat a squirrel.
And finally:
Gangplank should be able to make Amumu stop crying...because no matter what the problem was, Gangplank ate some oranges and it was k. 