ARAM, and how Riot basically broke it.
In all honesty, I play League mostly for the ARAMS. This being said, with the new advent of snowballs being added to Howling Abyss, it feels as if some champions who normally would suck, are dangerous as hell now, and champions who normally would dominate the abyss are now vulnerable as hell to dashes all throughout the game. Legend of the Poro King was fun... but these snowballs have to go, it's turned ARAM on it's head.