I thought I'd share my first modest hardware hack. (Sorry if this has already been done; I searched this forum and found nothing)
I took the shell of a (malfunctioning!) "square" ADB mouse, and the bottom of a Apple Pro mouse. The latter had a broken cord (common problem) and I had already disassembled it for repairing the cord.
This turned out to be very easy. All it took was to remove the top of the Pro Mouse, and making a nice oval hole in the ADB shell. Amazingly enough, the button hit straight onto the switch on the Pro Mouse!
Doesn't that look neat? And slightly odd.
It really fits that well!
Images are from this thread, in a swedish Mac forum where I first put them on display: