I took a 8-pin 12F683 PIC (PDIP) and wire-wrapped small, grasping clamps to each pin and then dipped the PIC into Plast-i-dip to waterproof it. This makes a great controller to drop into an existing electronic device or even to use underwater ;-)
Simple to reprogram by clamping to the USB programmer, then drop it into where you need it. An SOIC package would be even smaller!
Here is an old modem I dropped one into - it monitors what phone #s are dialled out, and if a busy signal is received, it automatically redials. Just had to find +5V, GND, and use the DB-25 connector pins out the back.
Another idea for this would be to open the case on a 'friend's PC, clamp this onto the keyboard or mouse connector, then periodically have the PIC wakeup, type random keystrokes or a funny message, then go back to sleep. They would toss out several keyboards before thinking to look inside the box!