The Stealth Gun was a specialized weapon that was invented and developed by the combined effort of the Militaires Sans Frontieres R&D department. It was a weapon that could fire a specialized ray that allowed a teammate to become optically invisible. It was designed shortly after the events of Metal Gear ZEKE's hijacking. Its bulky stature and the length of its ray allowed for it to be best used as a sniper rifle. However, it had a few shortcomings: Namely, it could only work if the soldier was actually engulfed in the ray, and its size couldn't allow for it to be used on the user, making it an exclusively CO-OPs weapon. Also, the device ran on batteries, so it had be used sparingly. MSF's R&D could extend its battery life, however.