Remove the shower head and place a chicken bouillon cube in it, then put the head back on.

 509

1  

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

 1103

1  

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

 592

3  

Fill someone's hair-dryer with baby powder.

 545

1  

Change the coffee in the office coffee maker to decaf.

 1089

1