I typed this out a while ago to play with my friends. I named them all too. Know that you've probably heard of a lot of these, but there are some cool ones in there. Now I will share:

Nazi Zombies Challenges

#01- Point Blank- Shotguns Only
#02- Quickdraw- Pistols Only...

I played this map with a few friends yesterday and some of us were invincible. We would get surrounded by zombies, only to have them do no damage. Is this a bug?