Make a Lockpick Gun with a HardDrive and old Mouse
Hack-A-Day has a link to instructions on how to make a lockpick gun out of nothing more than an old hard drive and a used mouse. And since lockpicks are mechanically the same thing as a tattoo gun (although slower and with a different tip) I bet you could use this for homemade body art as well.
-CGP fo Life-
