• At the end of the day, everyday, empty someone's stapler leaving only 2 or 3 staples. They will have to refill it everyday, and go crazy.
• Advertise a colleague's job as available. Leave their number with extension for contact. Be sure it is well paying and with low qualifications.
• Each day move a co-workers desk an inch.
• Drop a lemon slice or maraschino cherry into someone's water bottle.
• Spray glitter on anything.
• Move everything off someone's desk and into the office fridge.
• Play "Eye of the Tiger" everytime your boss walks in.
• Replace photos of friends and family with that of say Scott Baio, Eugene Levy, Drew Carey, William Shatner, or The New Kids on the Block. Also set their screen saver to a slideshow of these photos.
• Drop a rubber duckie into the watercooler when you are changing the bottle.
• Remove the ink from every one of their pens.
• Open a container of lice powder, and leave it in the bathroom. Say nothing to anyone. Panic will slowly rise.
• Put a brown paper bag in the office fridge labeled "squirrel"
• Before an important meeting, replace everything on a co-workers desk with the Hello-Kitty version or everything pink (pens with feather tops, pink pads, ...)
• Tape a really long memo or calendar to the inside door of the elevator.
• Install the Clapper on anything.

Most importantly, have fun and make sure you don't actually damage any property or your reputation. It's always best to prank friends and family, NOT someone you dislike. Never prank in hate.