John Malkovich's character in "In the Line of Fire" made a wooden gun capable of firing two bullets (before becoming worthless), and the Mythbusters made a duct

John Malkovich's character in "In the Line of Fire" made a wooden gun capable of firing two bullets (before becoming worthless), and the Mythbusters made a duct-tape cannon good for a few shots. I believe mass-produced street guns will be more cost effective and reliable for the foreseeable future. However, the likelihood of this being used as a reason to regulate 3D printing or 3D design files shouldn't be ignored.