I bought the Splinter Cell: Chaos Theory soundtrack from iTunes last night. A guy named Amon Tobin scored the game. He's kind of a techno guy, so a lot of people were skeptical whether it would sound right and fit into a game with a kind of non-melodious score, but I kind of like it. It seems to add to the tension, or at least it did in the demo.
If you want to hear samples from iTunes, click here.