The penultimate list of Free Linux games, with over 100 titles!
This list is a little old, so some of the links may not work anymore, but overall it's still a pretty solid compendium for any budget concious Linux (or Windows) gamer!
Know of a game that should be added to the list? Leave a comment below! _^
Sick of hats, nerfs, and other changes to TF2? Than Classic is for you! TF2 Classic is a resurrection of what the game was like in 2013, with restored gamemodes, guns, and classes
RTS set during the Bronze Age in the Ancient Near East. Manage a delicate balance between food surplus and the maintenance of your army - Multiplayer mode available
Turn-based 4X/RTS Strategy space colonization game - This is a commercial game that was open-sourced, you must compile the game from source code to obtain it for free. Consider buying it on Steam or GOG to support the devs
Inspired by Civilization, SimCity and Dwarf Fortress, Arcane Fortune is a game of empire building, diplomacy, conquest, construction, and deconstruction. Whether or not you build a utopia, or a hell on earth is entirely up to you
Famous RL that has both a City-builder/management sim mode, as well as a more traditional RL experience in adventurer mode (you can even visit the ruins of fortresses you've built in the sim mode)
Uniquely free to Linux users only. A tense roguelike that mixes stealth and arcade action. Explore the smouldering ruins of apocalyptic Basingstoke, UK, a world of extreme peril where reanimated undead and ferocious alien monsters roam!
a classic overhead run-and-gun from the DOS era updated for modern systems, supports up to 4 players in co-op and deathmatch modes - Installer Downloads
Minecraft clone written in C++ instead of Java for better performance. Base game is purposefully lacking in features, instead relying on mods from the community to flesh out the experience
A few personal recommendations here: Xonotic is the most engrossing quake clone I've ever played. The gameplay is fabulous and it would run on a potato. Definitely check it out if you like arena shooters.
Also people who bounced off FreeCiv for its somewhat dated mechanics (I believe it's most similar to Civ 2 in terms of gameplay), might enjoy Unciv. It's a FOSS porr of Civilization 5 and the last time I played it a few years back it appeared to be almost feature complete in terms of parity with its inspiration.
Lastly nethack is hard as nails and I've never been able to finish it. Good game though!