One of Bungie's posted screenshots of Halo 3 multiplayer footage is pretty awesome. It shows 1) the new Mongoose ATV vehicle in use by two players and 2) the new "laser rocket" weapon. A few details about these new, tasty goodies can be found here in this 1UP.com article. The screenshot is on the new "Valhalla" map. There are other hi-res screenshots on Bungie.net of Valhalla, High Ground, and Snowbound available here