Pet Peeves:
People who aren't paying attention when the light turns green. I count to one and blow the horn.
Left Lane Blockers. No explanation necessary.
People who can't stay in their lane when making turns. The line is there for a reason. I was pushed into a curb by one of these driving a USS Cadillac years ago.
The "cool" riders who have their seat in an impossible position and couldn't possibly control their car in an emergency. And the seatbelt won't work anyway.
Anyone who thinks they're the only car on the entire road. Changing lanes indiscriminately, stopping to look for wherever they are attempting to go in the middle of the street, braking for no reason, whatsoever, etc.
Anyone who slows down when the traffic in the lane next to them slows down and their lane is perfectly clear for the next billion miles.