Scid is a powerful chess database application with many search features. Its GUI makes entering chess games fast and easy, and you can search games by exact position, material, player names, and many other criteria. It does not come with any actual file of chess games, but it can convert databases to/from the popular PGN format which is widely used for chess games.
TEG is clone of 'Plan Tactico y Estrategico de la Guerra', which is a clone of Risk, a networked multiplayer turn-based strategy game. TEG is not fully compliant with Risk; some rules are different. It has a server, a robot, a GNOME client, support for GGZ Gaming Zone, and IPv6.
Universe is an Open-Source game which resembles Master Of Orion. It is written in Java. The goal is to have as few arbitrary limits as possible, allowing games as large as you wish. It also supports a concept called "Schemes" which allows programmers to develop distinct rule sets and extensions.
XBoard is a graphical chessboard for X that can serve as a user interface to play against any of a variety of chess engines that run on your local machine, or against human or computer opponents on an Internet chess server. XBoard can also be used by itself to read and write game files in PGN (portable game notation). WinBoard is a port of XBoard to Microsoft Win32.
Xscorch is a clone of the classic DOS game "Scorched Earth". The basic goal is to annihilate enemy tanks using overpowered guns. Players can purchase weapons and accessories to defend their tank, and they can attack enemy tanks by adjusting the angle of the tank's turret and the firing power. Xscorch supports gameplay with humans and computer AIs, and network gameplay is in development.
Crimson Fields is a tactical war game in the tradition of Battle Isle. Mission objectives range from defending strategically vital locations to simply destroying all enemy forces in the area. Tools are available to create custom maps and campaigns. The original Battle Isle maps can be played if the player has a copy of the game files.