The Chronicles of Riddick: Escape from Butcher Bay (Xbox, 2004)

This game just totally kicks butt. I'd say that it blends aspects of Halo (awesome first-person shooter action), Splinter Cell (stealth), and Grand Theft Auto (lots of missions to complete, usually below-level and for seedy characters like prison inmates), for a fully immersive gaming experience. The graphics are probably the best I have ever seen on Xbox, and the AI is extremely challenging to deal with -- the enemies are both intelligent and persistent.

Like Splinter Cell, the real challenge is to achieve your goals stealthily, but in many cases it's more fun to intentionally get detected and crack some skulls. Riddick has some serious finishers -- you can grab someone's rifle as they try to hit you with it or shoot you, and you end up pointing it at their head as they blow their own head off. You can also approach from behind and break someone's neck, slit their throat, bust their legs with a club, to name a few.

The characters in the game are constantly interacting with each other, so it can be very entertaining to listen to their conversations. It can also be beneficial to the player, as some key information, needed in order to complete some of the side missions, is learned this way.

I wish this game would have gone on forever -- I never got enough of it, and actually played it all over again once I got thru it. As others have noted, this game is extremely violent and contains (prominently) some foul language, so it's not for young children. BUY THIS GAME AND ENJOY!