There is also sweet tooth zombie which is easy. in order to get it you need to get flosser then get killed by a bear in any map (skin dont matter either)
You go to the shop and buy the flosser for 500 tickets in the survivor section then go into a match, you need to be a survivor. Then get killed by a bear. The map don't matter aswell as the bear. Then go to UC Zombies and you should have it.