americas army
America's Army, the Official U.S. Army Game (AA), provides young Americans with a virtual web-based environment in which they can explore Army career opportunities...
Übergame is a free open source, realism like, multi-purpose, multiplayer, casual, first-person-shooter game.
A truly free and open source multiplayer shooter, no strings attached. Have casual deathmatch matches on various scenarios. Build your own levels with the ingame editor and assets that come with the game, or just play around and use it as a sandbox.
games open-source-projects multiplayer shooter-game first-person-shooter