Designer and maker James R. Patrick has tried his hand at developing a 3D printed gun. Aside from the firing pin, which is a roofing nail, and the spring system, which he designed as made from rubber bands, the entire piece is 3D printed. The folks at FOSSCAD were intrigued by the idea and as part of testing it, substituted condoms for the rubber bands. It appears to be equally effective and a whole heck of a lot more entertaining. Read more about the condom-powered 3D printed gun in the full story: http://3dprint.com/66522/3d-printed-condom-hand-gun/
Below is the photo of Patrick's design, the Songbird gun: