Shia LaBeouf. I hate that guy. I think it's because no matter what I see him in, he's playing the exact same character, just in a different setting. Indiana Jones, Transformers, some Disney show he used to be on. Always the same annoying punk kid. If he showed some acting range, maybe I would give him a chance. Maybe.
I used to really like Kate Beckinsale, until I saw her in an interview. She came across as.. not very intelligent, and very boring. Perhaps I judge her unfairly, but I haven't been able to enjoy her work as much since. On the flip side, every time I see Alyson Hannigan do an interview, I love her more and more. That girl is awesome.
And I agree with Sky Breaker. There are some people (Paris Hilton) who have no reason to be in any spotlight.