The Battle for Wesnoth is a Free, turn-based tactical strategy game with a high fantasy theme, featuring both single-player, and online/hotseat multiplayer combat. Fight a desperate battle to reclaim the throne of Wesnoth, or take hand in any number of other adventures. Easily modifiable. You can even download other users' add-ons from the main menu.
Wesnoth 1.2.7 has been released. The main reason for this release was a security vulnerability of the multiplayer part. An invalid utf-8 string could make other clients crash.