Voice Chat system.
I love playing LOL and i find the ping system can helpful at times but also a little stiff. By this i mean that it would be nice if there were other ways of communicating in lol. I also play dota 2 and they have a voice chat system. It aint no stype were you chat away the whole game but simply just to say like "engage" or "back away" or "missing" stuff like that. This would add a good tool to the game that would not only help new players but add to the jungle role durring ganks and help solo top laners know when they need to hid under their turret. Anyways just an idea. Would be great if it was actually introduced, even if it was a new thing to come into the game in season 5.
Give lots of attention so RIOT sees it ;)