I go to see films because of who's in it. It's simple. We all have our favorite actors and their presence could well be the catalyst that pushes us to see a movie we may or may not have overlooked otherwise. A zombie flick might not initially be your cup of tea but hey, if Brad Pitt's starring, you might as well check it out. You've seen all of his other movies, you know he's an accomplished actor and well, if it's good enough for Brad then it's good enough of you. It's a security net for producers casting a big name will always draw in the crowds and make them that money back. However, Hollywood can't go on using Brad Pitt in every movie for the rest of time there needs to be an opportunity for new actors to break onto the scene. It's a bit of a gamble, casting 'unknowns' to share the screen next to your big-time A-listers. What if they're not up to it? What if the sheer pressure of working alongside a Clooney or a Cruise or a Dame Judi or a Sir Ian just a leaves them overshadowed as an actor and therefore, overshadowed as a character? It's a gamble, true. Here however, I have compiled a list of 10 actors and actresses who've been thrust into the limelight and come out on top. These people were unknown (at least by the popular masses) at the time of casting and undoubtedly raised a few eyebrows before the films release, but proverbially 'kicked ass' in their respective roles and built successful careers off the back of their big breaks.