The gun doesn't appear other than the mission and could only be accessed through cheats. It is the only silent handgun in the game and it has 100 rounds. A single dart will put an enemy to sleep quickly, incapacitating the enemy permanently. However, it is difficult to use because it requires close proximity, has a single dart in the magazine, and requires a long reload time. The Tranquilizer Dart Gun can be purchased for 5,000 Dollars in the single player store.