if I thought for long enough I could come up with a long list...
some I can think of:
- people not indicating properly at roundabouts esp 2 lane ones (people indicating right from the left lane when you're alongside them
then you realise they're actually going straight ahead... phew)
- people who don't cross the line while waiting to turn right at the lights. lights go red again and they stay put. have previously sat through 4 changes of lights without moving when people do that
- left-foot-brakers who ride the brake pedal so when following they effectively have no brake lights
- people tailgating while I'm obviously overtaking the slower traffic in the left lane and am already travelling maybe <5 over the limit
- people who flash you after you legally overtake them
- right lane hoggers on the highway/freeway
- people failing to maintain a constant speed and/or keep up with the flow of traffic, especially when they speed up as soon as you get to the overtaking lane and slow back down when it finishes
- seeing baby-on-board signs in peoples car windows... congratulations!!