I needed to fix my wife's surfboard, so obviously I built a sander. I needed a light duty machine with good balance and a large flat sanding surface. I wanted it to be cordless, so obviously, it had to also be brush-less. I eventually came up with something that looks like this:

From just the rite angle it looks like a motorcycle and it would be about the right size for a medium size rat, hence the name.
The part of this design that I'm the most fond of is the battery interface. I reverse engineered the battery interface from some of my cordless power-tool batteries, so now I can just slot in the battery of my cordless drill and off I go. It works really well and I think this will be my new default way of powering portable devices.