Tranquilizer guns are projectile weapons primarily used to fire a chemical to sedate others.
While the commandos chased Elisa, she was able to get one of their tranquilizer guns away from one commando she tripped and shot another commando with it.  The female commando tried to shoot Elisa with a tranquilizer dart, but missed.
When Maggie escaped from Gen-U-Tech, she was spotted by Brooklyn and Broadway on patrol. Xanatos’s commandos arrived and tried to tranquilize all three. Maggie surrendered and Brooklyn was hit by a tranquilizer dart in the back, prompting his and Broadway’s retreat. Sevarius later used a tranquilizer gun to fire a projectile at Derek Maza, but it was the mutagenic formula and not a sedative. Maggie was hit by tranquilizer dart fired by one the commandos when Goliath, Brooklyn and Lexington broke her out of Gen-U-Tech.
Xanatos shot Fox with a tranquilizer dart in her werefox form. She pulled out the dart and swatted the gun out of his hand. Owen then entered and shot her with a second dart. Due to her enhanced state, neither dart seemed to have an effect on her.
The tranquilizer guns came in all sizes. Sevarius, Demona, Taro, Xanatos, and his commandos used a handheld gun. However, the commandos once used a rifle that could fire particle beams as well. As stated above, Jason Canmore used a jet injector.
Although primarily used for sedatives, other chemicals could be used, as in Demona and Sevarius’s case, poison and mutagenic formula, respectively.
How the sedatives affected those injected varied. Elisa, a commando, and Kai fell unconscious within seconds. Goliath and Brooklyn were able to stay awake until their next stone sleep. Fox in her wereform was not affected at all. Greg Weisman muses that the effects on Goliath, at least, in his first encounter with the Xanatos's commandos was inconsistent simply because there had never been an opportunity to test the sedative on a gargoyle before.