Write a message on an upside-down paper cup that alludes to something horrible being trapped under it. Leave it on a coworker's desk or in a conference room.
 1479
1  

Change the coffee in the office coffee maker to decaf.
 1450
1  

Put tape over the optical sensor of someone's mouse.
 864
1  

Take a squirt gun into the rest room stall next to someone and shoot little drops over the wall every couple of seconds while pretending to pee.
 770
0  

April doesn't fool Chuck Norris, Chuck Norris fools April.
 851
0