Biting insects.
I itch for days, if not weeks.
Yappy dogs left outside by their owners
Neighbours who chip away for years instead of hiring power tools to do the job quickly (eg chipping up old concrete)
Posters who sneer at other posters who disagree and assume an air of superiority over those posters they consider intellectually inferior because they voted differently from them.
People who say Math instead of Maths