Plot: Chromium B.S.U. is an arcade-style, top-scrolling space shooter available on Windows, iPhone, PSP, Mac, AmigaOS 4, Linux and numerous other UNIX-like operating systems. It is a free software distributed under the Clarified Artistic License. Wikipedia
Plot: Globulation 2 is a real-time strategy game, available in beta as of January 2009. The game updates on an irregular release cycle and is available in many Linux distribution's package repositories. The game minimizes gaming micromanagement by automatically assigning tasks to units. Wikipedia
Plot: Scorched 3D is a free and open source artillery game modeled after the MS-DOS game Scorched Earth. Scorched 3D offers a new game-play approach compared to the 2D original, such as: fully destructible ... Wikipedia
Plot: Armagetron Advanced is a multiplayer snake game in 3D based on the light cycle sequence from the film Tron. It is available for Linux, macOS, Microsoft Windows, AmigaOS 4 and OpenBSD as free and open-source software. Wikipedia
Plot: Egoboo is a 3D open source dungeon crawling action role-playing game with support for Windows XP, Windows Vista, Linux, Mac OS X, and some earlier versions of Windows. Wikipedia