I know we're all fed up with W.W.2 games but after the lukewarm controversy in Modern Warfare 2 it might serve well to really fuck with the player and have some missions playing as a Nazi. Imagine the first mission, black and white schindlers list style to start out, you walk through the concentration camp following your commander. He takes you to a prisoner and the game forces you to execute him. It might be dark but I guarantee it'll sell faster than free £20 notes.