Beam Spam: The GCombat and Spacebuild Enhancement Project addons present many different ways to do this.

However, Nextbots are completely unable to jump by default, which often leaves them embarrassingly stuck on obstacles they could easily move around. NPCs that run on the Nextbot system tend to be quite smarter due to using navigation meshes (which are significantly easier to produce than a nodegraph).

By using the old game's AI as well, they end up blundering their way after the player even on maps that lacked noding.

One exception is the Retraux mod GmDoom, since it relies on the player providing a copy of the IWAD for Doom or Doom 2 to extract monsters and weapons from.

Or if the user downloads one of the several mods that allow manipulation of NPC behavior.

Artificial Stupidity: Most spawned NPCs will stand ramrod still, firing wildly at anything that comes nearby, unless the map they are spawned on is 'noded' properly to allow for complex AI.

Assets from other games can still be imported though, and Counter-Strike: Source is still a requirement for most addons unless you don't mind missing textures and models everywhere.

Artifact Title: Garry's Mod is not actually a mod anymore, it's a standalone game that can be run without Half-Life 2 or any other Source-powered game installed.

For example, a car battery will allow it to fire plasma rounds, a propane tank turns the weapon into a flamethrower, and it can even mimic specific weapons to a limited extent, such as the aforementioned gravity gun. The newest incarnation of the weapon has access to different modes of fire that are unlocked depending on what prop it absorbs.

One SWEP, named the 'Scavenger Cannon', is, essentially, the Rock-It Launcher - suck up any prop you want with it and then launch it, sort of like a rapid-fire gravity gun.

A mod of the already awesome molten rebar crossbow made it shoot sawblades.

In response, someone created a Baby SWEP that fired AK-47s, and another person made another AK-47 SWEP that could shoot either babies or sawblades.

The eponymous creator of the game, once scripted an AK-47 SWEP that shot babies as ammunition.

And let's not get started on the various SWEPs devised by the community. 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).

Gmod crashes when ing addons