Guns: According to New Scientist, the first working 3-D-printed gun was printed over the summer by a member of the AR15.com gun-enthusiast forum named HaveBlue. Actually, HaveBlue printed out parts of a gun, called the lower receiver, and combined them with parts of an ordinary pistol. House: Behrokh Khoshnevis, a professor at USC's engineering school, wants to build a 3-D printer so large, it'll spit out concrete to create a full-sized house quickly and affordably. His company Contour Crafting has been talking up the idea for nearly a decade, but its viability is still far in the future. Although Khoshnevis gave a TED talk (available on YouTube) on 3-D-printed buildings earlier this year, the closest we've gotten to seeing this in action is an animated cartoon on the company's site. Tamara Chuang is an outside contributor to TheStreet. Her opinions are her own. Email her at firstname.lastname@example.org and follow her on Twitter @gadgetress.