We've posted before about prisoners' inventions, including a tattoo gun machine made from an old walkman motor. (Link) Instructables now was step-by-step plans to make a similar DIY tattoo gun machine constructed from a remote control plane's motor, toothbrush, Bic Pen, and tape.
Link (via MAKE:)
UPDATE: Thanks to the readers who told me that it's not appropriate to call a tattoo machine a tattoo gun. Link And of course, if you want a tattoo, you really should go to a tattoo artist who uses professional equipment that's been appropriately sterilized.
UPDATE: BB pal Sean Bonner posted directions to make an even more, er, minimalist DIY tattoo machine out of hair clippers, a bic pen, and a guitar string. Link
