A great many things annoy me:
Ignorant people.
Snobby people.
Judgmental people.
Stupid people.
Impolite people with no manners.
Inconsiderate people.
People seem to have no self-awareness whatsoever.
Naive people.
People with more money than sense.
People who take no interest in politics.
So that concludes the 'people' section of my list, although I should basically say people in general because seriously, human beings are irritating. Dogs aren't irritating, they're nearly always happy and want to express their love. If people were dogs the world would be a better place.
General things that annoy me are:
Religious debates
Bad table manners
Badly decorated rooms
Bad music.
EDIT: I forgot, I also find unnecessary noise really annoying. I mean, that is actually the bane of my existence. An example of unnecessary noise is yelling when someone is 2 feet from you, slamming doors and general banging.