Autofill
Yikes. This is probably the most frustrating feature in matchmaking. But what's even worse about it, is that no one knows who was autofilled.
See, it happens often in ranked games, where people NEED to play their best roles in order not to mess up the game for everyone playing. Some people choose to speak up about it in champ select, and they are able to swap their roles to play their best one. But others, they choose not to say anything about it at all. Not until the enemy takes your inhib. Why is the teemo doing so bad against trynd? Turns out he was autofilled. And chose not to say ANYTHING until the game was clearly over.
This is something that riot can definitely improve, and it shouldn't be too difficult. All I ask is for something that would indicate in champ select when someone was autofilled, that way there is no unfair advantages in ranked.