Which actors are known in Hollywood as the most difficult to work with?

I'm curious; I LOVE acting and it's a passion. But I've heard some stories about some of the actors being really difficult to work with; but some seem like nice people. I'm not asking to be nosy by any means, but I'm just wondering, which actors are known in Hollywood as the most difficult to work with? My FAVORITE actor is Vince Vaughn and my FAVORITE actress is Rachel McAdams :) but lets hope one of those ones aren't difficult to work with though.