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

 1465

1  

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

 853

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.

 751

0  

Install the Blue Screen of Death screen-saver on someone's computer.

 816

3  

Place a pair of pants and shoes inside the only toilet stall in a rest room to make it appear someone is using it all day.

 744

1