Annie
I've been playing this game since early 2011 and I've always liked this game even though it's far from perfect. Most of the time frustratings pop up when some champions are just way too strong. They get nerfed and changed now and then but some of them keep being insanely strong.
One of the champions I'd recommend to be changed is Annie, the oneshot wonder. Her passive is the thing what bothers most people because Annie players just have to farm the stun and keep it until they can use it on an unlucky player. There is simply no skill, unless you see the fact her ultimate is a skillshot, in this champ. Why not make the PYROMANIA (passive) have a time on it to use? This will force Annie to use her stun or to do nothing at all. Nerfing her passive like this will make Annie players to time their abilities in order to use their combo.
I've played Annie alot b4 because she is so strong, there is really no skill to it.
Cheers