My biggest problem is when people can't seem to understand that turning lanes are for turning, and nothing else.
There is this one spot near me where this is a big problem, because on one side of the intersection its 3 lanes, but one of them is a turning lane, but on the other side its 3 lanes as well. So I always get in the middle lane and change lanes after the intersection because there "shouldn't" be anyone in that right lane because they should have turned, but I can't tell you how many times I've been marooned in the middle of the road waiting to get into the right lane because some asshole decided to blast right through the intersection.
I actually asked someone one time if they knew it was a turning lane and the guy replied to me "I don't care, as long at there is a road for my car to go to on the other side of the intersection I don't care what kind of lane I'm in."
And yield signs too, god damn these people...I'm getting angry now...