My biggest pet peeve is when people park on he wrong side of the road(facing the wrong way) first of all it is illegal. Second it is dangerous. And third are you really that friggin lazy that you cannot walk across the street or turn around and park on the right side of the street, really get a life. Also related to this is when people park on the sidewalk, it's called sidewalk for a reason.
For these people I will usually jamb their mirror when I walk by, my favorite is the manual mirrors as they can be a pain to change.