Drop Through Floor

Subject enters a typical office where someone familiar is sitting behind a desk across from the door. Everything in the room is fixed to the floor or walls and the person behind the desk is secretly strapped into the desk chair. As the subject approaches the desk to sit down in a chair he will eventually come to the center of the room at this time the floor of the entire room will flap open (either 4 triangular flaps or one major flap) and subject will fall 20 feet onto a air bag below

one up it: the fall is 40 feet onto a trapeze net.

two up it: the fall is into a water tank filled with sharks. (non-lethal)

Worst nightmare: Have the subject fall 20 feet into a foam pit which then has another trap door to an airbag or another foam pit.