Change the coffee in the office coffee maker to decaf.
1327
1
Put tape over the optical sensor of someone's mouse.
773
1
Find a sleeping person, fill their hand with shaving cream and then tickle their nose.
734
0
Hide all of the desktop icons on someone's computer and replace the monitor's wallpaper with a screen-shot of their desktop.
800
0
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.