Trimbandit's Scary Animated Zombie Groundbreaker Instructable uses two pneumatics to make a partially buried zombie jerk and pitch and seem to try to claw its way out of your lawn -- it's an incredibly effective illusion, one that capitalizes on the jerking, sudden motions of the pneumatic to lend a terrifying, otherworldly vigor that makes the mannequin skinned over the pneumatics seem like the living dead. *NOTE* I recommend starting with a low amount of pressure when testing and increasing from there until you are satisfied with the speed.