Grabbed this off the web a few years back. This one'll give you some ideas:
Demented Office Antics:
Points are awarded on a degree-of-difficulty basis, but you can award yourself extra points for creative execution:
One-point gags
Run one lap around the office at top speed
Groan out loud in the bathroom cubicle (at least one other "non player" must be in the bathroom at the time.)
Ignore the first five people who say "good morning" to you.
Phone someone in the office you barely know, leave your name, and say "Just called to say I can't talk right now. Bye."
To signal the end of a conversation, clamp your hands over your ears and grimace.
Two-point gags
When someone hands you a piece of paper, finger it and whisper huskily, "Mmm, that feels so good!"
Leave your zipper open for one hour. If anyone points it out, say, "Sorry, I really prefer it this way."
Walk sideways to the photocopier.
While riding an elevator, gasp dramatically every time the doors open.
Three-point gags
Say to your boss, "I like your style," and shoot him with double-barreled fingers.
Babble incoherently at a fellow employee, then ask, "Did you get all that? I don't want to have to repeat it."
Page yourself over the intercom (do not disguise your voice).
Kneel in front of the water cooler and drink directly from the nozzle (there must be a non-player within sight).
Shout random numbers while someone is counting.
Four-point gags
At the end of a meeting, suggest that, for once, it would be nice to conclude with the singing of the national anthem (extra points if you actually launch into it yourself).
Walk into a very busy person's office and, while they watch you with growing irritation, turn the light switch on/off 10 times.
For an hour, refer to everyone you speak to as "Bob."
Announce to everyone in a meeting that you "really have to go do number two."
While an office mate is out, move his or her chair into the elevator.
Five-point gags
In a meeting or crowded situation, slap your forehead repeatedly and utter, "Shut up, damn it, all of you just shut up!"
At lunchtime, get down on your knees and announce, "As God is my witness, I'll never go hungry again."
In a colleague's diary, write in, "10 a.m.: See how I look in tights."
Carry your keyboard over to your colleague and ask, "You wanna trade?"
Repeat the following conversation 10 times to the same person: "Do you hear that?" "What?" "Never mind, it's gone now."
Come to work in army fatigues and when asked why, say, "I can't talk about it."
Six-point gags
Posing as a maître d', call a colleague and tell him he's won a lunch for four at a local restaurant. Let him go.
Find the vacuum and start vacuuming around your desk.
Hang a two-foot-long piece of toilet roll from the back of your pants and act genuinely surprised when someone points it out.
Rollerblade around the floor throwing sweets.