^ I'd also add
Not following what the road signs say. I've seen so many times where someone will drive straight through in a curb lane that says no right turn execpt for buses. Or times where you can't not turn left at all or during certain times and they turn left.
Of course my answer to the left turners is to come up behind them and just lay on the horn and never let go and start yelling at them to get there piece of crap car moving. The best one was was this young girl who freaked out, went straight through and then cut off two lanes to make an immediate right.
I do believe that a lot of people should not be driving because they are actually scared behind the wheel.