Have you guys forgotten Time Survival? There should be rounds and after every round zombies get stronger, faster, and bulkier. You also should only be able to get the campain and Deadly Games guns.
Time Survival could use some more Nazi Zombies to it. Not the skin texture, I mean the dynamic of it's gameplay. Wave after wave with a group of players, and once you're dead you're out. It would be a pretty cool gameplay dynamic I think.