Despise might be a bit strong of a word, but people who piss me off to some degree:
-People who can't write/read properly despite having graduated High School (though I'm not sure who to be mad at, them or the school system).
-People who walk around with their iPod earbuds in and wander into traffic across roads (this happens a lot here in CA).
-People who talk about sports and only sports, as they can find no way to relate to people aside from how the Lakers or Dodgers are doing.
-People who create pointless OP's that we see on every goddamn forum on the internet.