I was playing Zombie Nazi mode yesterday with some buddies of mine, we rocked. Well only level 13 but it was insanely fun. :P What you want to do is get three men in the main room, and one in the hell room. After a round you just fix the barricades and go to the random box to hopefully get a big clipped machine gun, flamethrower, or ray gun. The ray gun is a one shot kill, and you will eventually get one from the random box, it doesn't matter if one person already got one.