hey i was looking around and i found these

http://www.gamespot.com/xbox360/action/halo3/screenindex.html

i also came across these that seem to be from campaign

http://screenshots.teamxbox.com/gallery/1353/Halo-3/p1/

one of these also shows a brute with an energy sword

http://media.xbox360.ign.com/media/734/734817/imgs_1.html

and as you see, it also shows that the mongoose is in halo3 and that a player can ride in the back of one

i thought they were getting rid of the smg or did they just change the starting weapon in multiplayer