Today is also Have Fun at Work Day...
1. If your target uses a powerbar with their computer try this one. Get a portable radio and plug it into the Powerbar. Turn off the powerbar then turn the radio volume to really loud. When they can't figure out why their computer has no power - they will turn on the power bar and get a big surprise.
2. Put a sign up that says, "Please use other door" Make sure to put signs up on all of your entrances or exits.
3. Whatever your target hates (Like a certian Sports Team or Politician) - post their entire office with posters or promo stuff celebrating that hated thing.
4. When they've left their desk, make a screen capture (print screen) of the person's desktop (or with a program open). Go into Windows Paint program and paste. Save as a bmp. Load the picture as the person's background. Sit back and watch them double clicking and rebooting fruitlessly. (Note: you can also create a bmp of an entire black screen and do the same. The mouse moves, but there's nothing to click on if you hide the icons!)..
5. Poke some small holes in the paper water cups so that next person that gets a drink of water will have some bonus sprinkles.
6. For co-workers who steal food....make cat food sandwiches and put them in the fridge. See what happens.
7. Try too much hot sauce or any other revolting ingredient for your food stealer.
8. Anonymously post quotes from Adolph Hitler on a company bulletin board. (Quotes about "team spirit" can be particularly inspiring.)
9. Adulterate other people's lunches: take bites out of sandwiches, sprinkle bacon bits in vegetarians' salads (also works well with Orthodox Jews), and spike the thermos of iced tea with grain alcohol.
10. Tell everyone but your target to bring a couple of changes of clothes to work. Then walk by your target with a different set of clothes on every time.
11. If you have a coworker that is extremely picky about the placement of their work materials, adjust them ever so slightly every day. It may be work tools, pens, supplies, computer monitor anything else in their work area.
12. Turn the volume on the speakers really loud on their computer.
13. Take anything you like from the target and make a ransom note for them to get it back. Works especially well if it is something is annoying or ugly and the target knows it.
14. Re-label the Data DVD’s - change the labels to read pornography type title’s like Debbie Does Dallas, or Girls Gone Wild
15. Hide in the supply closet and scare people when they open the door. 
16. Put a small radio in a ceiling panel close to the target’s desk. Just have it on loud enough so only they can hear it. When asked, Have you and your coworkers deny that they hear anything. If they mention that they really don’t like a certain radio personality or kind of music - that would be a good choice to turn the radio dial to.
17. Tape down the phone button on the phone so when the phone starts ringing and they pick it up it will keep ringing.
18. Page yourself over the office intercom, do not disguise your voice.
19. Tape or glue the items on your targets desk, to the desk.
20. Place a small washer and nut on top of a door hinge in a high traffic zone in a public building. Watch how different people react when they think they've broken the door.
21. Go to Microsoft word/ go to tools/ go to auto correct/ go to replace with/ change some popular words to “you smell” or the bosses name with "the funny guy".
22. If you have an office phone system that allows conference calling, you can prank two people at once. Call the first victim's extension, then very quickly call the second victim and push the conference button. Now both people will think the other person called them and will begin arguing over who called whom!
23. If he has an overhead bin style cabinet, layer the bottom with paper, then attach the paper to the door (with tape or something) so it comes out when the door to the cabinet is open. Then fill it with empty soda cans. When he opens the door to his cabinet, viola, all the cans will come crashing out and it will be most embarrassing for him.
24. Borrow the victim's cell phone when they aren't around and change the language setting to a foreign language. Then watch and laugh as they struggle to translate the setting instructions on their phone.
25. Dial the phone number of the guy in the next cubicle whenever he walks away from his desk. Hang up before he can run back to answer it. Repeat often.
26. Make some copies of a paperclip. Then put them into the paper tray of the copier. People will go nuts trying to find the paperclip stuck in the printer.
27. First, take out your friend's drawer. then tape a squeaky dog toy to the inside so that when you put it back and slide it in, it goes, "squeak squeak!" when it's squashed.
28. Tie a piece of cord under the victim's office chair to hold down the lever that adjusts the chair height. (When you sit on the chair it will slide all the way down, but as soon as you stand up the chair will rise all the way up.) All the ups and downs will drive the victim crazy.
29. Take all of the victim's paperclips and hook them together in one long string.
30. Place a piece of clear tape over the microphone part of the phone. Laugh as your victim struggles to talk to their callers.
See more work pranks, here
