Cell phones. When I see people driving and holding their cell to their ear, I just have this maddening urge to just ram my car into them and get the inevitable accident that is bound to happen (which sounds a little redundant, doesn't it?) over with. I don't own stock, but invest in a Bluetooth device, people!
Oh, and anyone who is wearing headphones or earplugs while they're driving, too. I'm almost certain that's against the law in some states, and if it isn't it should be!