Thief: The Dark Project.

It’s everything I could ever want.

• Excellent story perfectly meshed with the gameplay.
• A strange high-technology medieval world.
• Incredible level design combined with realistic roughly drawn maps, forcing you to take in your surroundings and build your own map.
• Variety of gameplay, ranging from infiltrating a rich baron’s mansion to rob them blind, to delving into ancient crypts filled with odd creatures and an alien culture for some adventurous tomb raiding, to some of the most terrifying pants filling survival horror I’ve yet encountered.

It is, in my opinion, perfection.