Here are some excellent games, which are Free Software. Most are released under the GNU GPL.
It might not seem that it is necessary for the games that we play to be Free Software. To some extent I agree that games are in a slightly different category. They are not entirely functional, they contain some elements that make them similar to novels or movies. However the portion that is software (the engine) should be free software, for the same reason that other functional software should be.
A practical example of the benefits of free software at work in the world of games is the large number of free software games that encourage the user to make their own levels, contribute their own artwork, etc. This allows even non-programmers to enjoy the feeling of modifying software to suit their needs.
- Digger Remastered A classic 2d arcade game in the style of pacman. You are a little mining car that has to collect all the emeralds to get to the next level. This game brought a lot of fun to otherwise boring 8086 PCs. There is a port to GNU/Linux which uses SDL. I have made a debian package, which you can download here.
- Kobo Deluxe Excellent 2d space shooter with nice graphics and support for OpenGL. Available for Gnu/Linux, Microsoft Windows and many other platforms. Fly around destroying enemy starbases. Insane number of levels. Based on Xkobo. Both Kobo Deluxe and Xkobo are available as Debian Packages (Xkobo also available for Hurd). GNU GPL License.
- PySol Solitaire game to end all others. Has tons of games. And tons of different sets of cards (even historical ones). And tons of options and sound and so on. Available for GNU/Linux and other platforms that support Python (I think Microsoft Windows is supported). Avalaible as a Debian package. GNU GPL License.
- sol.exe a simple solitaire game I wrote for the windows console. The zip file is 27k including source code. Now has mouse support. Read the README to see how to play.
- Mirror Magic Excellent oldschool 2d puzzle game for GNU/Linux, Microsoft, and many other platforms. Use mirrors to deflect a laser beem onto various targets. Based on many older games. Available as a Debian GNU/Linux package. GNU GPL License.
- Rocks & Diamonds Excellent oldschool 2d puzzle game for GNU/Linux, Microsoft, and many other platforms. Run around underground grabbing diamonds and emeralds, but avoid getting killed by stuff. Based on BoulderDash (or some such thing). Available as a Debian GNU/Linux package. GNU GPL License.
and also. The all-powerful ed has also contributed!.