I am of two minds on Cody Wilson and his Liberator, built by a 3D-printable CAD file and ABS plastic on a Dimension SST printer from printing firm Stratasys. I doubt Cody will use his gun in a crime, but should this technology be widespread, malicious actors will. And I imagine the Liberator is untraceable:
On the other hand/mind, I like freedom, rugged individualism, and self-reliance. Still, I see laws banning this sort of activity in our future, notably from Congressman Steve Israel.