The One-Peace is undisputedly the worlds simplest firearm. 
However, simple does not mean that it was not complex to develop. In part inspired by the American made Liberator of World War II, the One-Peace takes the same approach, but builds a firearm which is streamlined at every angle.

As said by Writier/Pilot Antoine de Saint-Exupéry "Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away" - There is no true perfection until minimalism is well understood, and the goal is achieved with just the bare essentials. The One-Peace is so bare that it's 3D model could be raw coded in less than 500 characters.

There is another Engineering saying that goes "The best part is no part, the best process is no process, it should weight nothing, cost nothing, break nothing."
 
The One-Peace consisting of only one main part, having a 99% polymer construction by volume, being under 160grams. 
There are no true moving parts, relying completely on compliant mechanics. All compliant mechanisms being endurance tested at over 1000 cycles before any wear or damage which effects the operation of the firearm. What is an all print in place - single piece design, requires no real post processing or machining.  It can be fired within minutes of removal from the printer. The only skills involved are having the ability to use a 3D printer, the One-Peace was designed to be able to be spit out of any machine, no matter how cheap. What is a single shot pistol currently chambered in .22 Long rifle, can be scaled up to other cartridges such as 9mm Parabellum, .32 ACP or .380 ACP. 
Material cost of production being less than 50 cents/ea, and at scale could be well below 10 cents/ea.
Currently still under testing, and development. 
 And Yes, It fires. Video below.