Lay between two nail beds and have concrete block broken on your chest. It's very impressive and not as dangerous as it might seem. Shows inertia and force per unit area.

Equipment
2 Wood Blocks with Nails		25lb Rubber Square		2 Wood block Seperators
Concrete Block		2 Books for Support		Carboard face Protection
Foam Leg Protection		Saftey Goggles		8lb Sledge Hammer