7. Katherine Heigl
Katherine Heigl has starred in a string of horribly mediocre and - at their core - very similar comedy movies over the past five years or so, all of which have proven one thing (apart from the fact that she should hire a new agent): Katherine Heigl isn't funny. At all. And aside from standing in front of the camera looking good and saying her lines with about as much enthusiasm as a light breeze on a winter's day, she almost always ends up feeling like somebody you'd later regret inviting to the party. Like, "why did we invite Katherine Heigl to this? She's such a bore." Presumably Katherine Heigl must have realised now that she isn't particularly amusing to watch on-screen, because that's something that nearly every review of one her movies spends at least a paragraph warning. In her personal life, though, Heigl takes herself way too seriously, and it comes through in her performances. She lacks comic timing and panache, and should go back to TV where she belongs. Not that there's anything wrong with TV, of course: she just isn't a movie star, let alone a comic one.