System Shock 2

Astonishing old school game, one of my all-time favorite game ever. Strong story, excellent voice cover, tense atmosphere, sharp music, endless respawning waves of blood-thirsty enemies, and their creepy voices/sounds, weapons that must be repaired every few minutes, brilliant upgrading skill system (that will force you to think more than twice), and finally, best villain ever:



I currently play on impossible difficulty as a marine.