Samuel L. Jackson – Iron Man

Where would a list of surprise cameos be without this game changer that Marvel threw out with the launching of their cinematic universe? Granted, Marvel didn't quite know how massive their franchise would become, but laying down the foundations of a shared universe in this post-credits scene with a star like Samuel L. Jackson as Nick Fury went a long way in building the kind of excitement needed to make it successful. It was a perfect tease to come at the end of a strong debut and only enticed audiences to see what was going to come next.