This papercraft is Solid Snake's Stun Knife, developed by the CIA, used by Solid Snake during Liquid Ocelot's Insurrection in 2014, based on the action-adventure stealth video game Metal Gear Solid 4: Guns of the Patriots (seventh title in the Metal Gear series), the paper model created by gankutsu-o-taku.
Stun Knife was able to be used directly as a stabbing weapon, or utilized for CQC. In addition, the Stun Knife had the ability to unleash a powerful yet non-lethal electric charge through the blade, allowing Snake to stun enemy soldiers instead of killing them. The electricity is generated from the back of the blade. This technique was used on Snake when Liquid Ocelot used CQC to force Snake to stab himself.
Upon recruiting Old Snake in Metal Gear Solid: Portable Ops Plus, the stun knife can also be procured. The Stun Knife's design was derived from the shocknife, which is a training knife, although without cutting ability.
You can download this papercraft model here: Metal Gear Solid 4: Guns of the Patriots - Solid Snake's Stun Knife Free Papercraft Download