System Shock 2 is an absolute classic, primarily due to it's use of atmosphere, lighting, and sound, hearing the mutterings of mutants. or the mechanical footsteps of a server droid all add to the feeling of unease. The fact that the game doesn't pause when you are in inventory mode adds to the fear, you can't be inventory managing while some mutants are bearing down on you. The isolation, with the story and world being built up by audio logs, it really adds to that sense of helplessness. In short, it has a great soundtrack, excellent acting, tremendous atmosphere and really has an excelent story despite the protagonist being the heroic mime variety with basically no reaction to the horrors going on around him. If you are looking for some classic sci fi horror, you should really check this out.
