Looking Glass Technologies' magnum opus
before 1998's acclaimed Thief
was a vast improvement over the earlier classics Ultima Underworld
series. One of the most sought-after underdogs of all time, System Shock
is sci-fi action/RPG at its best, featuring vast gameworld, gripping plot centered around a sentient computer gone awry, plenty of high-tech gadgets, and puzzles that integrate seamlessly with well-designed 3D levels. The only downsides are the less-than-intuitive controls and uninspiring cyberspace design. Otherwise, a true classic in every respect.
Note: you can download zip file of game maps here. Also, if you think you have done everything there is to do in the game, the excellent hacker's guide to sin will change your mind ;)