People who assume without knowing.
People who say things just to be the opposite of the majority.
People who are negative all the time.
People who can*t let go of a grudge or bad breakup or whatever.
Anyone who can*t think for themselves.
People who act like my best friend one minute and then hate me the next.
People who say anything you want to hear.
I could go on and on.
EDIT: In fact, I will...
Computers that don*t work.
Unsympathetic French teachers who still make you write during their lecture, despite not having a clue what it is they want you to write.
My horse*s stifle.
Mila Kunis (sometimes)
The fact that I can*t find That 70s Show in France.
Tuna (and baracuda, for those of you who know that story)