Thought I'd share a game that I've been playing off and on for quite a while now. It's called Mount and Blade and is a sort first person RPG combined with a strategy game. You create a character and run around a fantasy medieval world fighting ever larger bands of enemies in first person battles. 

This game is interesting for several reasons. First, it has a very compelling melee combat system, sort of similar to Oblivion and allowing for variety of fighting styles as well as ranged weapons (thrown, bow, crossbow, even firearms). The mounted combat is very good, and the first game I've played that even tries to model this. It's a lot of fun charging into enemy lines with your cavalry, or circling enemy forces at high speed firing your bow mongol style.

It also has an excellent mod system with a very active community of modders. I've tried several mods, and of course the quality varies but it's impressive to see the changes that can be made by modders to game system. I'm currently playing one called Lords and Realms.

You can get the game on Steam for $30 currently. There's also a free demo which I'd recommend - it's what originally got me to buy the game. There's a stand-alone expansion coming at the end of the month I believe, which sounds interesting!