A tranquilizer gun (or tranq gun) is a handheld firearm whose ammunition is non-lethal, and used to knock enemies unconscious. Tranquilizer guns in the Metal Gear Solid games include:
- M9 - a modified Beretta used by Solid Snake and Raiden in Metal Gear Solid: The Twin Snakes and Metal Gear Solid 2: Sons of Liberty, respectively.
- Mk22 - used by Naked Snake in Metal Gear Solid 3: Snake Eater, Big Boss and his resistance in Metal Gear Solid: Portable Ops, and the Militaires Sans Frontières in Metal Gear Solid: Peace Walker.
- EZ Gun - also used by Naked Snake in Metal Gear Solid 3 and Peace Walker, although in the latter, it appears as a special support item.
- Mk II pistol - used by Solid Snake in Metal Gear Solid 4: Guns of the Patriots
- Wu Silent Pistol - used by Big Boss and the MSF/Diamond Dogs in Metal Gear Solid V: Ground Zeroes and Metal Gear Solid V: The Phantom Pain.
Behind the scenes
In Portable Ops and Portable Ops Plus, the ammunition containers for the Mk22 and Mosin Nagant (9mm T and 7.62mm T, respectively) display a star and crescent, presumably to symbolize nighttime.
In Metal Gear Solid: HD Collection, hitting 100 soldiers with tranquilizers in Metal Gear Solid 2 will result in the unlocking of the achievement/trophy "Don't Taze Me, Bro."
On November 8, 2016, an update was issued that allowed for the development of the Anti-Tranq Agent. It is available under the security devices tab. It worked from grades 4 to 6.
- "Anti-tranquilization agent.
Stops tranquilizers up to a certain grade from circulating through the body over time."
- ―Anti-Tranq Agent description in Metal Gear Solid V: The Phantom Pain