Battle for Wesnoth
I've always been a fan of turned base strategy games. Mostly because I like the stategy part, it's like playing chess but with more variables and an imaginary world. The best of this would have been Warlords III for me, and it's nice to see just as enjoyable a game availabe as FOSS. I'm not much of a gamer, preferring to go out or play basketball, but fasting in Ramadhan provides a good opportunity to try some out.

The map is comprised of hexagons. It's set in a fantasy world, with your usual humans, elves, orcs, undead etc. One reason I like strategy based games is that it's not an all out race of who can build the most resources the fastest. Wesnoth stresses this even more, as there is an upkeep cost for units. So if you lose a few villages (income) you start losing gold real quick. When you start losing units, you don't have bold to recruit new units.
There are also numerous strategy elements in play. Terrain matters, so that elves fight better in woods. Night and day, such that lawful units fight better during the day, and of course evil fights better at night. The units are also well balanced, so that a powerful knight, can be quickly picked apart by archers. Another aspect that I like is that units gain experience, so it's wise to keep them alive as veteran units are more powerful.
There are multiple campaigns and they are challenging. You really have to plan it well, there are also turn limits. One scenario for example, I had to flank the enemy from both sides and assinate the leader from behind. Otherwise, their forces would just hold you until your turns run out.
The artwork is not too bad, and it is constantly being updated/improved. You won't find final fantasy like cut scenes, but the games doesn't lack polish.

If you're into strategy games, I highly recommend this. It is availble on most platforms, Linux, Windows, Mac and FreeBSD.
Spring
I was a fan of the RTS game Total Annihilation, and the good news is that the game engine has been done in 3D and it's FOSS. The Linux port is under way, and apparently Linux to Linux games are currently working.
With ATI open sourcing/releasing specs for their drivers, we should finally get great high performance 3D video drivers on Linux soon.
