There is a song that when I hear it or the name of the song, (which is very often due to its name), it gets stuck in my head and I can't get it out untill I start brainwashing myself with another. Surprisingly that new song dissapears when this song does, so that is good at least. The song is Zombie by The Cranberries. It is mainly the chorus that repeats itself. But since I haven't posted 50 posts yet I can't posit the youtube video here... -_-
Like East above, Happy gets stuck in my head if I hear it at work. It stays with me until I get home and I will usually start humming it while doing something at which point my roommate will start throwing Cheetos or M&M's at me until I stop. He hates it just as much as I do.
Two songs by this duo were played almost every night in the late 80's in gay clubs. I was not a fan, but they were somehow annoying stuck in my head for two or three days after going to a club.