Highly Moddable! Fan Patched! has it's own Complete mod for basic play. This is a modder play ground. Call of Chernobyl is the ground work for most mods. Check out MISERY, Anomaly, & soon Ray of Hope!

Highly Moddable! Fan Patched! This game is a buggy mess unmodded. Clear Sky Complete is the most Common "Patch" for the game. Not as many mods as SoC or CoP but still a few good ones like MYSTERY.

Highly Moddable! Fan Patched! This game is a buggy mess unmodded. STALKER Complete 2012 is the most common way to "patch" it. Check out Moddb for TONS of mods like Lost Alpha and Autumn Aurora 2!

Kinda Moddable! Fan Patched! The Unofficial fan patch is a must to play. Based on the source engine so it is moddable but it is tricky. There are quite a few awesome mods for this on Moddb!

Fan Patched! While not very moddable outside of making maps it is fan patched! Turn off save gems and AI companions and the game is the true Quake 2!

Is a Mod! Map Editor! Steam Workshop support! what if portal had a gel gun and not a portal gun? has a map editor like Portal 2. Gameplay based off of the student project Tag the Power of Paint.

Mostly Moddable! Steam Workshop support! Make money from mods! Mod zeds don't seem to be a thing here unlike the first game. You can have cosmetic mods submitted to be added to the game. Custom maps!

Highly Moddable! Was a mod! Steam Workshop support! Want new zeds? new maps? new modes even? they are all there! Started life as a mod for UT 2004.

Highly Moddable! Steam Workshop support! The mod tools are built right in the game and can be accessed from the main menu!

Mostly Moddable! Almost all of the mods that started here moved to Arma 3 but there are still a few good ones like the fact that DayZ started here. Just get Arma 3 for the mods.