GNU Backgammon

GNU Backgammon (gnubg) is for playing and analysing backgammon positions, games and matches. It's based on a neural network. In the past twelve months it has made enormous progress. It currently plays at about the level of a championship flight tournament player. Depending on its parameters and its luck in recent games, it rates from around 1900 to 2000 on FIBS, the First Internet Backgammon Server -- at its strongest, it ranks in the top 5 of over 6000 rated players there) and is gradually improving; it should be somewhat stronger than this when released. Since almost all of the CPU time required during supervised training is spent performing rollouts, and rollouts can easily be performed in parallel, it is hoped that users will be able to pool rollout results and collectively train it to a level stronger than any individual could obtain.

download here:   http://www.gnubg.org/index.php?itemid=22

Cube 2: Sauerbraten

Cube 2: Sauerbraten 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).

dot3 labs is a company started by the creators of Sauerbraten that offers commercial support.

Authors, feature list and more: see the reference documentation or the wiki.

download here:   http://cubeengine.com/files.php4

Neverball

Tilt the floor to roll a ball through an obstacle course before time runs out. Neverball is part puzzle game, part action game, and entirely a test of skill.
Also found here is Neverputt, a hot-seat multiplayer miniature golf game, built on the physics and graphics engine of Neverball.
Neverball and Neverputt are both known to run under Linux, Win2K/XP, FreeBSD, and Mac OSX. Hardware accelerated OpenGL is required. A 500MHz processor is recommended.

download here:   http://neverball.org/download.php

Frozen Bubble

Colorful 3D rendered penguin animations, 100 levels of 1p game, hours and hours of 2p game, nights and nights of 2p/3p/4p/5p game over LAN or Internet, a level-editor, 3 professional quality digital soundtracks, 15 stereo sound effects, 8 unique graphical transition effects, 8 unique logo eye-candies.

You really need this game.

download here:    http://www.frozen-bubble.org/downloads/

PlaneShift

PlaneShift is a Role Playing Game immersed into a 3D virtual fantasy world which is FULLY FREE to play. Fully free means you will have no surprises of premium content which will limit your gameplay or unbalance the game. There are no limitations in skills, ranks, abilities, items you can gain with your free account. There are no time limits or additional constraints. Other similar games just advertize the "free" concept to sell you premium accounts. We don't. Servers and bandwidth will be donated by sponsors.PlaneShift is made by a group of RPG enthusiasts and not by a commercial company. This allows us to expand the game wihout any constraint or limitation.PlaneShift is Open Source for the client and server code, so everyone can contribute to its development!

download here:   http://www.planeshift.it/download.html

Hexen II: Hammer of Thyrion

In 2000, Raven Software released the source code to their class based shooter game Hexen II and its multiplayer extension HexenWorld. Since then, there has been some source ports of this game, such as the now discontinued Anvil of Thyrion project, but nothing has been done for Linux since the beginning of 2002.

The Hammer of Thyrion project is a cross-platform source port effort: We continue the development for Linux, BSD and Mac OS X people, with continued support for Windows users as well. Many bugs are fixed and even new features are added: New sound modes, improved mouse handling, improved video modes, OpenGL glows and more. You can go to our project page for more information.

download here:   http://uhexen2.sourceforge.net/

Unles: Lunar Expedition Simulator

The Unmanned Lunar Expedition Simulator is a small 3D (OpenGL) game in which you control an unmanned moon vehicle. It is a two-player game that may be played either against the computer or against another player on the internet. There are two game modes: a racing game and a death-match game.
Technical stuff: The game uses rigid-body-dynamics for control of vehicle movement. It has a particle system based gun, 3D audio, and an online high-score list.

download here:   http://unles.sourceforge.net/download.html