Spare Change

On Der Riese go in front of any perk machine and lie down. You will get 25 points (take that extraneous zero!).

Zombie Magnets

On any map (not sure about NDU as it only has 1 grenade spot) go to any perk machine/? box/grenade outline/Betties outline (not regular weapon outline). It works best if you rub your back on it while pressing X.

Alternately, just run into them hard (machine will make a collision noise). The longer you stay and rub against it, the more zombies will want to play.

If it works, some/all of the nearby zombies will run for the wall icon/perk machine/? box instead of chasing you.

A good spot is by the revive soda machine on Der Riese. Slam into it, jump into the hole, rub your back against the back of the tunnel (radio is there) and/or the grenade wall icon. As you come out of the tunnel, lots of zombies will run into the tunnel past you.