Go to a store, go the the candy section, and place the candy bars in the wrong place.
Go to a store, go to the magazines, get a research magazine and dump it in the child's toy section
Take a dump in the sink in the bathroom
Go into the bathroom, wait til someone comes in, stand on the toilet making sure that person cant see you, make scary sounds like whisper or something scary.
Buy a soda, finish it, fill it with piss, leave it somewhere
Print a fake parking ticket, place it on a car in the parking lot.