Fill a very large glass full of water, tell a friend to place their hands on a table (palms down), put the glass on top of one hand and ask if it hurts, when they say "no" tell them to put one hand on top of the other, place the glass on top of both hands, and ask, "Does it hurt now?" then walk away. Put some money on the floor. When the target goes to pick it up have a small piece of cloth that you can rip. If you time it right, the target will think the worst. Wet a tissue with milk and run around holding the tissue to your eye pretending you stuck your pen in your eye, when somebody comes close, squeeze the tissue to make the Milk spurt out all over the place. Tell everyone but your target to bring a couple of changes of clothes to school/work. Then walk by your target with a different set of clothes on every time.