Pull on a coworker is to press ctrl+print screen on their workstation, then paste it into Paint, save the pic, and set it as the desktop background. Move all of their icons to the trash. When they get back to their desk, clicking won't accomplish anything!
Hide all of the desktop icons on someone's computer and replace the monitor's wallpaper with a screen-shot of their desktop.
Put tape over the optical sensor of someone's mouse.
Change the coffee in the office coffee maker to decaf.
Put a "Please Use Other Door" sign on the entrance to your office building if it only has one entrance.
Install the Blue Screen of Death screen-saver on someone's computer.
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.
The 21st century: Deleting history is more important than making it.
April doesn't fool Chuck Norris, Chuck Norris fools April.
Chuck Norris keyboard doesn't need a delete button.
Q: What did the dentist say to the computer? A: This won't hurt a byte