Awesome / Garry's Mod

Garry's Mod is a nigh-unlimited sandbox game, so it has a lot of moments that are extremely cool.

The base game

• Prop surfing. Just place a prop (preferably a big one) under your feet, drag it with the Physgun, and fly. Noclip is more practical, but flying on a microwave is much more fun.
• Building a successful rocket using thrusters can be extremely fun, even if you will eventually hit the map's ceiling.

Mods

• The Star Wars Lightsabers mod. It's not just a generic melee SWEP, as you can cut through practically anything. It's incredibly high-quality, allowing the player to cycle through various Force powers while wielding the blade. The sabers are incredibly customizable too, even allowing you to use Darth Maul's double-bladed saberstaff.
  • Taken to the logical extreme with Lightsaber/Jedi System, which allows players to perform full-on lightsaber duels.
• The Hoverboards mod, made by the same creator as the Lightsaber mod, allows you to ride on a similarly customizable Hover Board. You can turn off the thrusters midair and do various tricks.
• Despite Source's map size limit, someone still managed to make an infinite map using clever rendering tricks. You can even go to space and visit Spacebuild-style planets. You can watch the creator explain how he made it HERE.
  • The creator of the Infinite Map also made Seamless Portals. It allows you to either spawn them in or use a Portal gun.
• There is a mod called Xala's Movie Helper, where it is a collection of dozens of optimizable settings to help animators in making their machinimas, including among other things, green-screening the skybox, hiding the viewmodel, changing the FOV, and making NPCs make automatic actions, and a lot of other things.
• Cinematic Camera is a mod for a more advanced camera tool that allows the player to not only help film videos with better effects, but they are able to make it look like a Found Footage film as well, with the special effects and overlays that it has, including [[Letterbox letterboxing]], film grain, color filters, shaky cam, and even a camcorder overlay!
• The mod MW19 Tactical Infiltration is a mod for when the player respawns, they respawn in the helicopter from Call of Duty: Modern Warfare (2019), they even rappel from it!
  • There is a separate mod that allows you to respawn in the van from the same game, and another mod that allows you to respawn in the plane from Call of Duty: Warzone, with the entire plane-jump scene in full recreation. Unfortunately, it requires the map to have built in HDR, though. But still, these "Infil" mods make you feel like an badass hero on an important mission.
• There's a gamemode that puts Team Fortress 2 into GMod. You can switch between playing as either the mercenaries or a regular player.
• The Media Player allows you and any friends to watch videos and movies in the game, even outside the designated Cinema gamemode.
• There are recreations of gm_construct and gm_flatgrass in 2D. The maps were slightly adjusted to make it work, and the former uses teleporters so that you can visit all of the areas in the map.
  • You can also play through the first world of Super Mario Bros.
• The ANP Units +PLUS+ series, including the Rebel Units +PLUS+ and the Combine Units +PLUS+ as of now, each have a collection of custom Half-Life 2-themed SNPCs that wouldn't be too far out of place in the setting. The Rebel Units for example, have armored and heavy rebels, and support units such as engineers and scouts (No, not the TF2 kinds) for example, and grenadiers, flamethrower units, and communicators. There are even Rebel Scanners, rebel Combine Soldiers and rebel Metrocops, former Spetznaz soldiers that would be appropriate given HL2's setting in Eastern Europe, and a three-NPC "Raider" faction that are their own third party. The Combine Units, however, have more kinds of soldiers such as Supressors, HL2 Beta NPCs such as Assassins, Cremators, Wasteland Scanners, Proto Striders, and Proto Stalkers. There are also bosses, armored units, medics, mines, Synth Soldiers, and more turrets and APCs. There's even a Invasion mode where you have to fight off waves by waves of Combine too.
• Don't have any friends wanting to play GMod with you? Way too worried about multiplayer? Look no further than the Zeta Player nextbots, near perfect recreations of standard players if you want to turn a singleplayer game into the full experience.
  • The creator of Zeta Players has come out with the sequel: Lambda Players. It has the same idea, but Lambda Players is much more optimized and customizable, due to the addition of module systems.
• There's several fully playable versions of the Five Nights at Freddy's games on the Workshop, one of which was made mere days after the first game released!

Maps

• The map Union City is set in a fictional area of New York City. It is extremely well designed, and it has a really nice artistic style, almost realistic looking actually, not to mention that you can enter into most of the buildings.

Dupes

• The Mono Wheel is extremely fast and easy to use.
• Most of the low/zero gravity cube dupes on the Workshop. Just throw a grenade up to them and watch what happens.