We did this several years ago on a gardening forum I belong to, and it was really fun to see what bothered other people, and what didn't.
What absolutely drives me crazy are people who cannot park straight in a parking spot, and think that it's fine to be over the line. Or even worse - the huge trucks who think it's fine to take up FOUR parking spots right up front because they're oh-so-much-bigger than other cars around them...
So... what is your worst pet peeve???