It seems the newest patch for Black Ops 2 on Xbox 360 accidentally activated the Ray Gun Mark II in Zombies early. You can already use this gun in all maps in the Zombies mode. This gun is supposed to be released as part of the new Vengeance DLC set to release on July 2nd.
UPDATE: It appears a hotfix went out this morning to remove it from the game. Expect it to return on July 2nd…
Here’s a video posted by OMGItsAliA showing the new Ray Gun Mark II in action in Zombies:
Here’s another video showing the Ray Gun Mark II Pack a Punch’d via ImJustChucky: