Make Your Own USB Powered Gadget

I've found my weekend project. Maximum PC has published 9 awesome DIY projects, one of them being the steps to turn different gadgets into USB powered ones. They teach you how to make a USB powered fan or book light.

I'm thinking my blowdryer would fry my computer, but I have always wanted to make my electric toothbrush USB powered. Thoughts on what you would try to do? [Maximum PC]