Well aside from the obvious in Keanu Reeves or an actress for looks rather than talent, I'd also say Ben Affleck. I think he is maybe the worst thing to hit film since the romantic comedy (well not all of them are bad but ya get me). Pretty much if I see a movie, and he is accredited in any way, something must be wrong. Aside from Good Will Hunting, which I just have to get him out of my mind, he is just bad.