Battle Tanks
Battle Tanks is a free and open source fast 2D tank arcade game with multiplayer mode and split screen
FreeCol
FreeCol is a free and open source turn-based strategy game based on the old Colonization game and similar to Civilization
Globulation 2
Globulation 2 is a free and open source, multi-platform, innovative Real-Time Strategy (RTS) game which reduces micro-management by automatically assigning tasks to units
Freeciv
Freeciv is a free and open source, multi-platform empire building strategy game inspired by the history of human civilization
Warzone 2100
Warzone 2100 is a free and open source, multi-platform multiplayer 3D real-time strategy game
LinCity-NG
LinCity-NG is a free and open source, multi-platform city simulation game and economic strategy, a polished and improved version of the classic LinCity game
UFO: Alien Invasion
UFO: Alien Invasion is a free and open source, multi-platform, real-time strategy and tactical role-playing game
C-Dogs SDL
C-Dogs SDL is a free and open source, multi-platform run-and-gun game in which players work together during missions and against each other in a “deathmatch” mode
Crispy Doom
Crispy Doom is a free and open source port of Doom with enhanced-resolution, limit-removing, based on Chocolate Doom
Tux Football
Tux Football is a free and open source, multiplatform 2D football game in an arcade style