Tranquiliser guns are weapons built and designed by the Tau'ri. They are non-lethal weapons, as their main purpose is to knock out their enemies alive, so they can be easily captured.
The guns were used to knock out The Touched after they discovered a cure for the disease. They were later used to capture Apophis after encountering him in the Nox homeworld. However, the darts failed to pass Apophis' personal sheild. Later, when Hathor took over the SGC by controlling the men in the base, Carter and O'Neill used the guns to knock out the SFs guarding her. (SG1: "The Broca Divide", "The Nox", "Hathor")