Call of Duty's distinguishing features, by and large, can't be considered innovations--that's too strong of a word. However, this is a game that pulls together many of the best aspects of other, similar games, and also includes all sorts of little "wish-list items" that may have crossed your mind while playing those other games. The result seems, above all, very well designed. The action in Call of Duty, ultimately, is arcadelike--much like in Allied Assault or Battlefield 1942. You can't survive a shot to the head, but you can take a few bullets anywhere else and can keep going just fine.