At long last and 'with gracious permission from Valve,' Garry's Mod now contains 'most of Counter-Strike: Source and Half-Life 2 Episodic content' even if you don't own those games

A contorted face of Dr. Breen in Half-Life 2 and Garry's Mod.

So long, pink checkerboards that represent missing textures! Adiós, pitch-black skies that signify an absent skybox! Don't let the door hit you on the way out, enormous 3D model that says ERROR where a car should be!

Those have been common sights for users of Garry's Mod for, oh, let's see… 20 years or so? And one of the biggest culprits for those missing textures and models is that players didn't own the games that those assets were pulled from: Half-Life 2's episodic entries and Counter-Strike: Source. You could join a community map that used assets from those games, but if you didn't own them, you would get an eyeful of pink and black or that big ol' ERROR sign.