Domino Theory
Crystal Dynamics
Does COD MP have anything that would work well in Halo?
An ESRB rating that's worthy of its M status. There isn't a single thing in any Halo game to date that is worthy of being an M rated game. There's more shooting and graphical deaths in Viva Piñata.
Another is the frame rate, although, an XBLA title like Dungeon Defenders can handle 1000+ enemies on-screen at once without a single drop.