I am aware that COD games from Call of Duty 4 and on that there has been a 3rd game mode (ie. Spec Ops, Nazi Zombies, Arcade) What kind would you expect in Call Of Duty 7?
Me, personally would a "Tower Defense" like structure. Call in airstrikes or place machine gun turrets all those stuff. Maybe throw in a nuke in there. Basically like Nazi Zombies but you order equipment.