Narq-dart pistol
From Halopedia, the Halo wiki
The Narq-dart Pistol is a nonlethal United Nations Space Command ground firearm.
It was used by the Spartan-IIs during their training on Reach when they were around 12 years old. The weapon was issued to the Spartan-IIs by CPO Mendez when they were fighting Tango Company in Capture the Flag. The pistol uses compressed air to fire a narq-dart capsule. The effective range is 20 meters (60 feet), and on impact it could drop a rhino in its tracks.
