pepperspray on the car door handle is my favorite.
Brilliant! My worst was scotch tape over the infared mouse. 
Well, if office pranks are accepted:
-Any computer savvy person can advise you as to which files you can delete or modify which will aggravate him without bringing work to a standstill. Which computer applications does he use?
-Whenever a fluorescent tube starts buzzing anywhere in the building, switch it with a good one from the boss’s office.
-Occasional “ripe” items hidden in his office. Switch plates can be removed from electrical outlets (be careful!) to allow access to drop items within a wall.
-Remove a little bit of a table leg, just enough to give a little wobble.
-Remove things from his office, then replace them.
-In general, make his office an annoyance.
I’m still in favor of the golf thing. If he leaves his golf bag in the office while he is gone for an extended period of time, bring his clubs to the pro shop, and have every club shortened by an inch or two.
Fill his hovercraft with eels.
What does this mean, please?
Leaving a bowel movement in the upper water tank of the toilet, instead of the toilet bowl.
Would it work if the oil were poured on the tail pipe, too? Not very many engines are accessible without breaking into the car.
This one worked especially well in college, when everyone had papers to write. It might still work in some offices.
In MS Word, change the font on your boss’ computer to white, on all his important documents. Leave the docs there, just make it look like they’re all empty.
Good for a heart attack, at least!
Or, along the same lines as Stargazer suggests, record new macros for all his function keys.
If anyone in the office has any leftover medication prescribed for a urinary tract infection (the kind of med that turns the patient’s urine blue), it’s kinda fun to drop a tablet or two in the weiner head’s coffee.
It’s pretty much assured that after his next trip to the can you’ll see him leaving the building in a big hurry on his way to the doctor.
Fantasies I had for my old boss, who paged me late one night to ask how to turn on the screen light on his Blackberry, then paged me a few minutes later to ask how to turn it off, among other things. Please note these are probably illegal and should not be attempted by anyone, at any time.
Preface for #1 and #2 - he was Canadian, eh, and flew back and forth between Chicago and Toronto.
#1 - Drive to Indiana and buy a bunch of firecrackers. Open and sprinkle the gunpowder on the carpet under his desk, so it gets all in his shoes and socks. He goes to the airport, takes off shoes, and the sniffer machine picks up the gunpowder.
#2 - Buy large amount of pot, sprinkle on carpet under his desk, so it gets all in his shoes and socks. Airport + drug sniffing dogs = hilarity!
#3 - Go to porno shop, get a bunch of subscription cards for the magazines, and fill out with his name and work address.
Please tell me your boss’s boss has stepped in and fired the twit.
Note to self: do not piss off 5que…
I think if you are gonna put some old food in his office–go with strawberries. They won’t really be smelly, so he won’t be looking too hard for them, but as I recall from college they draw fruit flies in a couple hours. Maybe hide them Friday afternoon after he has left and close up his office. By Monday his office will be crazy with little flies.
Buy a bunch of little cartons of milk, and then open them. Hide them around his office. Nothing reeks like sour milk.
Is he married? Have some young sounding woman call his wife and demand she (the wife) leave him since the caller and the boss obviously love each other more.
Or, have someone call his wife and tell her that the boss is cheating on her, and since the caller had been in cheated in the past before, the caller thought that the wife should know.
Back in high school, we did this to a guy with every mail back post card we could find. I would only do ones for free information, and didn’t do magazine subscription cards, but other people did. This guy was receiving scores or sometimes hundreds of letters a day.
Along the lines of subscription cards: if someone else opens his mail (and many boss-type people have their secretaries open their mail before they ever see it), you can request some free samples of stuff over the web and have it sent to his work address. This could start a nice gossip chain going about him. Kick off the campaign with Astroglide and Trojans (links go to “request a sample” pages).
Not sure it’s worth destroying the guy’s marriage… Or his wife’s, who may be a fine human being who never did anything wrong but fall in love with a selfish prick.
This is one I just came up with today and it’s so incredibly evil, I feel compelled to put it in spoiler boxes so that small children and women of delicate constitution can avoid it.
Find out his home phone number, and then advertise it everywhere as a suicide hotline number.
Duuuuude! Word!!!
Don’t just do that. But -
Post it only in bathrooms of country clubs, and golf courses.