SOME of The human vehicles in Halo 2:
*wathog
*ATV
*junglehog
*snowhog
*troophog
(i.e) The wathog is the same as in the first games except it looks better. I don't like it but there will be an ATV(with no weapon on it) in Halo 2. The all new junglehog is painted in camo. color and has bars over the driver side door and wind-shield. and the troophog is totally covered and carries up to 6 marines at once!

A.I./alien race
Bungie is working on the marines A.I so instead of seeing one marine say I'm going in, cover me! they'll work up there own strategy withuot the Master chiefs help or cortana's! In Halo 2 you will fight a new alien race called the Brutes which supposedly act like the flood in some ways, but you will also still fight covenant aliens to. I found this info. at: www.computerandvideogames.com