What started off as a mod has evolved into a standalone game and one of the most highly immersive ones as well..........

User Rating: 10 | Garry's Mod PC
The Source engine is still running beautifully. GMOD's graphics are still very pleasing. Singleplayer, surprisingly, doesn't get stale very fast. Ragdoll posing is fun and is seen in a lot of Youtube videos. There are a lot of things that you can make and add-ons are a great way to extend the fun.

Multiplayer, specifically Trouble in Terrorist Town, is a true jewel. Plenty of game modes are available, with lots of servers to play those on. TTT is the most popular gamemode, and is like a video-game version of Clue. DarkRP is another fun gametype as well. Sandbox is also prominent in Mp, though not as much. The Steam WorkShop has tons of mods to keep you entertained as well.

The community is still very active, which is great for a nearly 8 year old game. You will have very little trouble finding a good server. There are many truly brilliant community-made maps that are found in GMOD.