don't want to play online, but have no idea what to do in singleplayer? open sandbox after a re-install, but quickly get bored? this is for you. a friend asked me once "how are you playing gmod singleplayer in (current year) for longer than 20 minutes" here's how introduction gmods defining feature is its customisability, and it's both its greatest strength and its greatest weakness. outside of pre-existing game-modes and servers, the onus is on the player to make up their own fun. however both of those options are limited, with the majority of servers being only a handful of popular game-modes, and singleplayer game-modes being generally scarce. for the longest time i didn't care for this game, but in recent months its quickly become one of my favourites because i built up a set of mods that, for me personally, made the game click. this guide will go over those mods, and general ideas for more structured gameplay that you might not have considered a populated sandbox this is a set of mods that brings the sandbox mode closer to your conventional 'sandbox' game like GTA. https://steamcommunity.com/sharedfiles/filedetails/?id=2341497926&searchtext=background+NPCs this mod adds NPCs that spawn naturally around the map, complete with a wanted system that will spawn more combine the more civilians you kill. this works on any map, and can easily be customised or toggled on and off. it brings the maps to life and gives you things to interact with. https://steamcommunity.com/sharedfiles/filedetails/?id=2243186467 adds natural weapon spawns, which both makes the weapons feel more exciting to get, and makes exploring the maps more meaningful. you do have to manually add all of your weapons to the mods' spawnlist, but you only have to do this once and can easily add new weapons as you go. https://steamcommunity.com/sharedfiles/filedetails/?id=1587455087 allows you to create custom nav routes that will spawn vehicles along them when enabled. personally, its not worth it since you have to make the route manually, although a few maps have saves that add them for you. but its worth including if you're willing to go through the trouble pseudo-deathmatch theres no shortage of deathmatch game-modes for gmod, however most of them don't have any form of bots, and are usually restricted in their content anyway. these mods, combined with customisable entity spawner, let you play a sort of deathmatch on any map, with any models and weapons (provided you don't care about keeping score) https://steamcommunity.com/sharedfiles/filedetails/?id=2773405248 this adds respawning player-like bots to the game. by default they behave like sandbox server players, running around and building things. however you can configure them in their options menu to never build and only ever attack, and they make pretty fun opponents. the map does need a navmesh for them to work, but if it doesn't have one you can just type nav_generate into the developer console to make one automatically. https://steamcommunity.com/sharedfiles/filedetails/?id=2895802066 this mod is exactly as it sounds, and is very versatile. this is if you want a clear end-point, and don't want to just stop whenever you get bored. horde survival https://steamcommunity.com/sharedfiles/filedetails/?id=2939410311 a very customisable mod that lets you have any NPCs spawn in increasingly difficult waves, with the win condition being surviving whatever you set the last wave number to be. https://steamcommunity.com/sharedfiles/filedetails/?id=597017711&searchtext=zinv if you don't want a limited amount of waves, and just want NPCs spawning in infinitely, this is a good alternative. racing with a good vehicle mod installed and some good maps, gmod is a surprisingly solid racing game. my personal choice is S-cars, since it has very fun albeit janky handling, but simfphys is also a popular option. https://steamcommunity.com/workshop/filedetails/?id=104483020 more importantly, s-cars has a checkpoint spawner tool. this lets you create and save races, with customisable lap counts that will keep track of your time, turning basically any map into a race track. unfortunately, loading the checkpoints from a save seems bugged. it remembers the checkpoint placement, but the functionality to start the race doesn't work. this might just be my install, though. misc beyond those things, theres plenty of other singleplayer gameplay thats more structured. singleplayer maps can offer quite a lot, ranging from linear half-life style shooting levels to more exploration focused horror or story maps. if you own other source engine games, you can also usually play through those maps in gmod. and saves can re-work existing maps to have some sort of objective. be wary that the majority of these are low-quality, but there are definitely some fun ones. end hopefully this guide gave you some ideas of things you can do in this game beyond spawning 200 zombies then uninstalling there are enough mods out there that you can tailor the game to make it whatever you want it to be, you just have to do some digging and mess around with settings until you're satisfied.