The Nickname Game
Give all of your co-workers a lame nickname such as Poncho, Chachi, Gumby, etc. Then always refer to them by this name.

Awww, how cute!
Always include a piece of your child's artwork as the cover page for the reports you write.

Meeting At 4:24 PM
Schedule a meeting for 4:24PM. Then after everyone arrives, tell them they can go home.

Company Xmas Party
Volunter yourself to organize the company xmas party. Then choose to have the party at McDonald's Playland. Feel free to charge everyone $15.

If anyone needs me...
Send everyone at the office an email to let them know what you are doing. For example: "If anyone needs me, I will be in the copy room"

The 'OK' Nod
It doesn't matter what anybody asks, always reply with an 'OK' and a nod.

IN
Put the trash bin on your desk and label it with "IN".

Moldy Coffee
Grow mold in your coffee mug.

Headphone Prank
Whenever someone comes in your office, put your headphones on and talk loudly. Then remove your headphones as soon as they leave.

I Think My Phone Is Ringing
During a conversation, tell your co-worker(s) that you think your phone is ringing, even if you are a long way from your desk. Then leave and go and get some coffee.