Over the course of E3, Halo: Reach developer Bungie did mention in interviews that the Firefight game mode would return. They even said matchmaking would be part of the experience and there would be lots of customization options.
What they didn’t show us was the game in action, so here you go. Grunts, Jackyls, Brutes, and Elites.

Also: the “BlackEye” Skull is gone. Hoorah!