Here's a pet peave of mine:

when you're walking and approaching a crosswalk and someone in a car stops to let you by when you're not even to the street yet. If they just kept driving, they would've passed by before you even got to the crosswalk, but instead you have to wave to them and pretend to hurry across the street. Awkward

:edit: and on a similar note, people who don't take their right of way at a four-way stop sign. It's your turn dammit, this is no time to be polite! :madr: