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.

 814

0  

Put a "Please Use Other Door" sign on the entrance to your office building if it only has one entrance.

 1556

1  

Fill someone's hair-dryer with baby powder.

 803

1  

Hide an alarm clock in someone's bedroom and set it for 3:00 a.m.

 843

0  

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

 917

1