I have to admit, this sounds like fun. Wouldn't you just love-love-LOVE to get your coworker with a paintball land mine that's filled up with Liquid Paper or Cool Whip? Oh yeah, I can see this in my future.
The RAP4 land mine is only $65 and it's rechargable so you can re-use it time and again. It makes a loud noise (as you would expect) and of course blows whatever liquid you fill it with all over the place.
The best part is, it works for good friends as well as foes. And, I know just the person to try this on...oh yes, I am evil!
Note: these "land mines" are filled with CO2 cartridges and used in paintball wars. In theory, nobody gets hurt with them, so quityerbitchin.
hat tip: Wired magazine