The Tool Gun is an important piece of Garry's Mod. It allows players to manipulate a variety of functions to create different things. The gun itself looks like a revolver with lots of technical wiring and a screen on the back, displaying the tool being used. Also, items in the GUI menu can be spawned using this.
The Tool Gun uses the sounds of the pulse cannon from the Airboat in Half Life 2.
If looked at closely, you can see random text written on the LCD screen, like "You have not crashed! Click here to crash!"