Here's a gun from a 3D printer that finally won't get everyone's panties in a bunch.
Redditor and obvious Halo fan halodeacon96 showed off a small gallery of images of a pistol replica from the Xbox original, Halo: Combat Evolved, made using a 3D printer.
The pistol, or "M6D Personal Defense Weapon System" if you wanna be snooty about it, was a fan favorite of Halo: Combat Evolved in both the game's campaign and multiplayer modes, due to the fact that it was powerful, so much so that it wound up nerfed in the Halo sequels. It's alleged that there was an internal debate about how powerful the M6D should have been. As a pistol, it was supposed to be weaker, but an employee made a last-minute code change that gave the pistol its power. In addition, it came equipped with a with a mid-level scope, which coupled with its high rate of fire made it quite versatile as well.
It was capable of killing a fully shielded player in three shots to the head, a Flood Combat Form with one shot to the opening of the chest, and could even take out a Hunter on Legendary mode in one shot, provided you nailed the exposed back.
The replica is fairly accurate in size ratio as the game gun would appear in reality, measuring 27cm long, and 17cm from the bottom of the handle up to the barrel. Granted, it's cheaper than buying a replica, costing about $150 to print. But if you own a 3D printer which can cost well into 5 figures, a pithy $150 is mere pocketchange (if you fall into this category, lemme know if you happen to be hiring, wink wink).
Halodeacon96 didn't say where he got, or who designed the .cad file used for the gun, but if you do a little searching, you'll be sure to come across something eventually.