Many Tablet PC's contain a gyroscope. I wasn't aware that the one I have (a Toshiba Portégé) also contains one. After activating the Toshiba Accelerometer tool, I'm now able to open my Start menu or switch between the different applications by "shaking" my Tablet PC. Usefulness: probably not that high, I guess; coolness: really high...

If you have a Toshiba Portégé, you can enable this functionality by going through the Start menu to "Toshiba", then "Tablet PC" and then "Setup for Accelerometer Utilities". Note that this path can be different on your Toshiba Tablet PC. After you click this shortcut, you'll probably see the following application.