Get in an elevator and stand motionless facing a corner until it's time to get off.
Go to a grocery store and stand next to the frozen section. when someone opens the door start singing " ice ice baby."
When a person opens a door stand behind the door and bang your hand on the door and act like you banged you head on the door.
Call someone and say is mr wall there, is mrs wall there and if they say no then say how does your ceiling stand if no walls are there.
Ring someones doorbell fast and keep doing it until they answer the door. When they answer, just stand there and don't talk. See how long they'll last
Go to a store with automatic doors. Stand near them and make them open and close without being seen.
Lie on the sidewalk and if anyone stops and tries to get you up, stand up, and walk away.
Play ding dong ditch without the ditching. See how long you can make the other person stand there.
Have a better idea for this list? Send it on in!