The tranq (tranquilizer) gun is a non-lethal firearm that is used on numerous occasions throughout the series.
The tranq gun has been used by multiple people and multiple organizations over the course of the show, mostly in order to capture or incapacitate others. It is a popular choice for John Casey, as he is quick to tranq others, mostly on missions where he is required to keep his presence a secret, however he is occasionally convinced not to use them by Chuck.
Although he prefers not to resort to violence, the tranq gun is Chuck's weapon of choice, since it is non-lethal. Chuck has shown great skill with the tranq gun, especially when used with the Intersect 2.0. Although he was ridiculed for using one by the Ring Director, Chuck continues to make it the only firearm he will employ when given the choice.
The tranq darts are usually strong enough to knock a person out for multiple hours with only one dart, however some people take multiple darts in order to be knocked out by them. John Casey and Jeff Barnes have been shown to need multiple darts to be knocked out by them, mostly due to Jeff's past with multiple drugs and Casey's history of being exposed to truth serums, tranq darts, and other drugs throughout the spy world. Rock star Tyler Martin was able to wake up after only a short time of being knocked out, due to his years of drinking, drug use and his fast basal metabolism. Tyler, in fact, enjoyed the experience, and was looking to repeat it.
By season 4 the tranq gun has also become Morgan's weapon of choice on missions, due to it being non-lethal and his inability to properly fire a hand gun.
The tranq gun fires darts that release a tranquilizing agent on contact. Although the most common tranq darts have red feathers on their end, there are different kinds of darts used with the tranq gun. Some darts are more potent than others, and some are even able to make the victim forget any events within 5 minutes before being shot. Despite the multiple differences between darts, none have shown to have any long term negative effects. All of them can be also used manually in hand-to-hand combat by stabbing them into an opponent through his exposed skin or a thin dress.