Doom 3
 

If you haven't played it, play it. It's one of Rator's top ten games that you must play in your lifetime. You do need a capable PC (I cannot comment on the Xbox version). One of the most beautiful, well put together, well thought out games ever.

Bear in mind it IS just a first person shooter. It DOES pull out all the stops , ie: exploding barrels, shitloads of monsters to shoot, etc. But the story is cool, and it leads you thru very well. Get it.

I concur on DOOM 3 , it rocks.