QuantZ, is a "unique puzzle action game" based on physics, where your goal will be to control a three-dimensional object positioned at the center of the screen. Balls that gravitate around can be eliminated by shooting them into balls of the same color.
Tremulous is a free, open source game for Windows, Linux and MacOSX (unofficial version for Mac OSX) based on the ioquake3 game engine, that blends a team based FPS with elements of an RTS. Players can choose from 2 unique races, aliens and humans.
PlayOnLinux is a free application that puts an easy to follow wizard style interface on top of WINE and contains some pre-installed scripts to help load a number of compatible applications and games.
D2X-XL is an OpenGL mod for the classic 3D game Descent 2. D2X-XL is based on D2X 0.2.6, has all bugs from D2X 0.2.6 fixed and has restored all features from the original D2_3dfx (official Voodoo graphics version). D2X-XL is free and runs on Windows, Linux and Mac OSX.
Smokin' Guns is a free, open source first person shooter game for Windows and Linux that takes you back to the times of sheriffs and bank robbers in the legendary Wild West.
Warzone 2100 is a free, real-time strategy and real-time tactics hybrid computer game for Windows, Linux and Mac OSX which offers campaign, tutorial, multi-player and single-player skirmish game modes, unit designer, unit experience system, and everything you would expect from a modern RTS game.
Just days after the release of Nexuiz 2.5.2 that brought many new features to this popular open-source game, Alien Arena 7.31 is out.
The developers of Nexuiz, a great free, open-source Windows, Linux and MacOSX game released version 2.5.2.
Glest is a free 3D real-time strategy game for Windows and Linux, where you control the armies of two different factions: Tech, which is mainly composed of warriors and mechanical devices, and Magic, that prefers mages and summoned creatures in the battlefield.
Blood Frontier is a free and open source single and multi-player first-person shooter game built on a complete remake of Cube Engine 2, which lends itself toward a balanced gameplay, completely at the control of map makers, while maintaining a general theme of tactics and low gravity.
Djl is an open-source (GPL licensed) game manager written in Python 2.5 for the GNU/Linux Operating Systems, inspired by Valve's Steam software for Windows for which anyone can submit games.
Urban Terror™ is a free-to-play multiplayer first person shooter game for for Windows, Linux and Mac OS X. It's a mod for Quake 3 Arena but it doesn't require it anymore, as it can run on ioquake3. Unfortunately Urban Terror is closed source, even though ioquake3 is under a GPL license, but that doesn't mean you can't play it.
Regnum Online is a free fantasy massively multiplayer online role-playing game (MMORPG) game (although premium content is available for enhanced game play) which runs on both Windows and Linux and I must say it looks really good.
I recently bumped into a cool RTS (real time strategy) game for Linux called Hive Rise. Although the game is not open-source, it offers a free Linux download as a RUN file which can easily be installed on your Ubuntu box. To install it in Ubuntu, you only need to follow these steps:
World of Padman (or WoP for short) features a cartoon-style approach, with maps, characters, weapons and sounds all based upon the Padman animation series.
VDrift, TORCS and SuperTuxKart are 3 free, open source car racing games which run on Windows, Linux and MacOSX.
In this article I'll overview Cube 2: Sauerbraten, an open-source shooter running on Linux, which also provides a gaming engine for developing FPS games.
Following the article on configuring Urban Terror, a popular first-person shooter game based on the ioQuake3 engine, here is a guide for configuring the original ioQuake3 game, including customisation of cvars, using new maps, weapons and characters models, and more.