In the new Nazi Zombie map Ascension there are a few new things. First the Gersch Device.
The Gersch Device creates a small singularity event sucking any nearby zombies in, awarding the player 50 points per zombie. You can jump into the black hole which will randomly teleport you to any spot you have opened.
One of the Ascension achievements involves "Killing 5 zombies with one Gersch Device". It fills up the player's Tactical grenade slot. It's basically the new 'Monkey Bombs.'
Second new weapon is the Matryoshka Doll.
It replaces the player's tactical grenade slot, and the player gets three of them. When thrown, they act as a cluster bomb, exploding four times. Most often, one doll will explode into two, one of which will deploy another. This is contrary to the nature of the dolls, and what common sense would dedicate the weapon's action to be. Its usefulness can be hindered by its random nature of explosions, resulting in the possibility of the grenade thrower harming himself; however, this is remedied by using the PhD Flopper perk, which makes a player immune to their own explosives. If a player already has the Gersch Device in their inventory, the Matryoshka Dolls will replace them, and vice-versa. The player cannot have both the Gersch Device and the dolls since they are both special grenades.
There are a few new types of zombies as well in Ascension. The military zombies can now do a barrel roll and dodge bullets. And there are new Space Monkeys that replace the Hellhounds, once you buy a perk they start coming every round to steal it.
Here are a few pictures of the map.
(These are the new Lunar Landers that take place of the teleporter in Kino Der Toten)
For more information visit http://callofduty.wikia.com/wiki/Ascension.