Okay, time for another. This one is for practically every modern computing platform.
Battle for Wesnoth (
http://www.wesnoth.org/) is an open source community game closely resembling games like
Ogre Battle,
Master of Monsters, or even the more popular
Final Fantasy Tactics. In any case, whatever game it reminds you of, you kill your opponents through a string of scenarios, retaining your corps from each encounter (a la
Myth). It's a fun game with a punishing AI that has decent graphics and is continually getting better.
Oh, and it's free.