People that use cruise control set at 65 in the left lane and won't get over regardless how many cars pass them in the right-hand lane.
...this one really irks me, I will flash my brights and give them a chance to move over, if not, pass on the right and give them the scowl (no finger or fist)

Sitting in traffic with your air conditioner broke and having to smell diesel fumes from a pickup truck that obviously isn't used for work. Small appendage syndrome, I would guess.
...hey now, I have a diesel