irrlamb is a platform game, in which the player moves a ball through a 3D terrain, it involves a lot of physics and challenging gameplay!

Secret Maryo Chronicles is an Open Source two-dimensional platform game with a style designed similar to classic sidescroller games.

Alien Arena a fast and frantic first person shooter that combines the best of gameplay from games like Unreal Tournament and Quake III.

Savage: The Battle for Newerth is a fantasy/science fiction computer game that combines aspects of Real-time strategy and First-person shooter into one game. The producers of the game define it as a ‘Real Time Strategy Shooter’, or ‘RTSS’. It takes place in the far future when man has (after an apocalypse) rebuilt society, but is threatened by intelligent beasts.

The Battle for Wesnoth is a turn-based strategy game with a fantasy theme. Fight a desperate battle to reclaim the throne of Wesnoth, or take hand in any number of other adventures.

Open Yahtzee is an open-source version of the classic dice game Yahtzee. It is built to work across many different operating systems and platforms.

Sauerbraten (a.k.a. Cube 2) is a free multiplayer/singleplayer FPS, built as a major redesign of the Cube FPS. The aim of this game is to allow map/geometry editing to be done dynamically in-game, to create fun gameplay and an elegant engine

Nexuiz focuses on bringing the FPS genre back to the basics with quick, lethal battles and balanced weaponry. As of the current release there are 9 weapons and 24 official maps, as well as 15 player models, with an average of 2 skins each.

Tremulous blends a team based FPS with elements of an RTS. Players can choose from 2 unique races, aliens and humans. Players on both teams are able to build working structures in-game like an RTS.

Frets on Fire is a Finnish music video game created by Unreal Voodoo in which players use the keyboard to play along with scrolling on-screen musical notes to complete a song, and is a clone of the Guitar Hero video game series.

LinCity-NG is a 3D City building Simulation Game for Linux-based operating systems. It is a polished and improved version of the classic LinCity game.

FlightGear is an open-source, multi-platform, cooperative flight simulator project featuring 20, 000 real world airports, correct runway markings and placements, world scenary, accurate terrain and more.