The folks at Treyarch announced this weekend on GameTrailers TV (I was out all weekend and just watched the show) that Call of Duty: World at War
will have a zombie mode that's unlocked after you finish the single player campaign. You and up to three friends are stuck in a building and must survive ever increasing waves of Nazi zombies. The mode sounds pretty cool as you will have time to rebuild your defenses between waves of zombies. The episode also covered the new death cards that you can unlock during the game to unlock different game modes.
I have to admit that I'm starting to warm up to the game a bit more as Treyarch is going all out for this one. I know it probably won't exceed Call of Duty 4 but it does sound like they are cranking all kinds of stuff into the game.