When you plan to turn left or go straight at a four way intersection, and a guy in a giant truck goes to take a turn and they pull so far out in front of you that you can't see incoming traffic. I mean, come on! He's got a venerable watchtower seat and he feels the need to go the extra four feet to block the view!
Also, angsty teenagers who feel the need to bolt down the sidewalk at night on their bikes, while wearing black, oblivious to the fact that I might be trying to get out of the parking lot. Now that I think about it, there're a lot of things that bug me...
Okay, one more, one more... That one awkward parking spot that looks fine at first, but when you try to back out later you realize the sign, or the garden, or whatever else could occupy the space, is taking up a huge chunk of the spot behind you, so you're stuck in this twilight zone spot where it's impossible to back out even though you somehow made it in.