Here's one I've not heard of before! Quetoo (originally Quake2World) [Official Site], a free and open source FPS that's currently in Beta is asking for votes on Steam Greenlight.
The source is under the GPL, but some artwork and sounds are under different licenses. You can find it on github here and license information here.
- 11 Quake-inspired weapon choices, from shotguns to lightning dispensers
- 17 maps made by their team - some favourites ported from their inspired sources (Quake, Quake II), some original maps made specially for Quetoo, and more to come
- User-generated content. Like most Quake-based games, you can add/replace models, maps, and even make your own code mods! They plan to support Steam Workshop as well, and provide extensive tutorials on their content generation utilities
- Many ways to play. Free-for-all, team deathmatch, match mode, CTF, instagib, all built into the base game!
Give it a vote if you like the look of it.
About the author - Liam Dawe