Zombie ambush on Der Riese
This trick requires two players. After a few waves pass, open the doors that lead to the Thompson and go up the stairs that take you to the power switch. Open the door that leads to the teleporter, then go to the right and have one player go to the wall on the left. There is a hole on the floor. Have a player remain as close as possible facing the window and look at the door every once in awhile. Note: You must be squatting down. Have the other player go in the hole and stay close to the wall near the other player. The zombies will go in but they will not get near you. When all the zombies are there, move slightly forward and they will start to approach. Shoot some and move back to keep them away.