You can build prop cannons that can shoot everything from sawblades to watermelons. One of the sample scripted weapons (or SWEPs in community jargon) included with the game, the Flechette Gun, is exactly like the USP from Half-Life 2 only it shoots an endless stream of the exploding rounds fired by the Hunter enemy from Half-Life 2: Episode 2. GMod Tower (discontinued succeeded by Tower Unite, which does not use GMod at all).
