Another application of the gamelayer in the world of education is already in use at a number of schools, including Princeton University (Priebatsch attended Princeton for a year, and then dropped out).
Having a lead character that was of Native American descent let me delve into an original world of traditional instruments as well as percussive chanting, helping to create a new layer of storytelling within the game.
Shield and ammo management are just as important as they are in the campaign (and in every Halo game) and these considerations add another layer of strategy to the equation, for better or worse depending on your predicament.