Pedestrians who don't acknowledge vehicles that stop to let them cross at a zebra crossing. Normally twats with headphones on. And I speak as a pedestrian who acknowledges vehicles on BOTH sides of the road who stop for me, or who even visibly slow down for me. It's makes everybody's day go a...
Or as the great John Dowie once put it...
'The Dutch, the Dutch
I hate them worse than dogs.
They live in fookin windmills
And they mince around in clogs.'