Bungie just held their panel at San Diego Comic-Con where they've revealed a new mode for Firefight that lets you play as the Covenant while others will be playing as Spartans. Another new mode -- called "Gruntpocalypse" -- has you up against waves of Grunts. Additionally, all of the maps for Firefight will be taken from the single-player campaign.
Another addition to Halo: Reach is Forge 2.0 and it's going to offer you a lot more customization features than ever before. Don't like that rock? Take it out then! Yup, you now have control over a map's scenery along with the bases. Teleporters can be manipulated to any size too and you can have vehicles get teleported through, including the newly revealed Fork Lift. Yes, a Fork Lift. It beeps when you back it up. Yup.
[Via Halo: Waypoint's Twitter]