When I was in school, we once used a potato to power a clock. I remember being completely fascinated by this, since a food product could actually produce electricity on its own. Well one young girl at the Aperture Labs took this idea a bit further, and harnessed the power of a potato to create PotatOS.
This has to be one of my new favorite Thinkgeek products. They give you the PotatOS unit, and everything you need to attach it to a real potato. When you get it all hooked up, it will light up and speak 17 clips from Portal 2. Sadly, the device isn’t actually powered by the potato, (they only generate a small bit of power) but it does only work when it detects that it is connected to a potato. $30 is a small price to pay for this Portal collectable, especially when there’s science to be done.