The Princess Bride (successive people use the identity of the Dread Pirate Roberts)
Most spy novels and films - For example, James Bond uses numerous fake identities
http://www.bondmovies.com/alias.shtmlAlso the Peter Sellers / Woody Allan
Casino Royale film in which everyone is called James Bond!
Several instances of Death taking on a human identity in various genres, e.g. the film Meet Joe Black, a couple of instances in Sandman comics spinoffs, Bill Door in the Discworld novels.
Tom Riddle AKA Lord Voldemort
