Showing software for all platforms
Sauerbraten (a.k.a. Cube 2) is a free multiplayer/singleplayer first person shooter, built as a major redesign of the Cube FPS. Much like the original Cube, the aim of this game is not necessarily to produce the most features & eyecandy possible, but rather to allow map/geometry editing to be done dynamically in-game, to create fun gameplay and an elegant engine. The engine supporting the game is entirely original in code & design, and its code is Open Source (ZLIB license, read the docs for more on how you can use the engine).
AssaultCube is a FREE multiplayer first-person shooter game, based on the CUBE engine. Taking place in realistic environments, with fast, arcade gameplay, it's addictive and fun! With efficient bandwidth usage, it's low-latency and can even run over a 56Kbps connection. It's tiny too, weighing in at a lightweight 40 MB package available for Windows, Mac and Linux. On the correct settings, it can even run on old hardware (Pentium III and above).
OpenLieroX is an addictive real-time Worms 2-D shoot-em-up backed by an active gamers community. It features online play; customizable weapons, levels, and characters; and dozens of levels and mods. The game is based on a deathmatch setting, where multiple players face off in a closed level. Each player is equipped with five weapons selected out of all the weapons allowed, and with a ninja rope that allows the player to move in any direction. Players begin with a set amount of lives, and while the game records the number of kills, the last man standing is usually considered the winner. LieroX also allows team deathmatches, which has made it common for players to form clans.
BZFlag is a free online cross-platform multiplayer 3-D tank battle game. The name originates from "Battle Zone capture the Flag." It runs on Windows, Mac OS X, Linux, *BSD, Irix, and many other platforms.
Paintball 2 is a fast-paced virtual paintball game based on the Quake2 engine, with capture the flag, elimination, siege, and deathmatch (free-for-all) styles of gameplay. Players are split into two teams, armed with paintball guns, and head out to capture the other team's flag. One shot knocks a player out, and players must wait 60 seconds to respawn. To win a round, you must knock out the entire enemy team.
Egoboo is an action-based adventure game in which you slay foul monsters, explore unusual locations, and get lots of loot. Your difficult and dangerous quest is to save Lord Bishop, the king of the land, from the evil Dracolich.