The Original ThinkGeek Annoy-a-tron would be useless against an army of
The Annoy-a-tron generates a short (but very annoying, hence the name) beep every few minutes. Your unsuspecting target will have a hard time 'timing' the location of the sound because the beeps will vary in intervals ranging from 2 to 8 minutes. The 2kHz sound is generically annoying enough, but if you really really want to aggravate somebody, select the 12 kHz sound. Trust us. The higher frequency and slight 'electronic noise' built into that soundbyte will make a full-grown Admin wonder where his packets are.
Assuming you have done your part in selecting a suitable hiding location for the Annoy-a-tron, it will do its part to drive your co-workers slowly mad with its short and seemingly random beeps. And when someone does locate the Annoy-a-tron, they're really not going to know what it is - which is almost as much fun as watching them search for it. Muahaha.
The Annoy-a-tron takes one CR2032 battery (included) and measures approximately: 2.5" x 1.25" x .3". It will run for 3 to 4 weeks on a single battery.