TNM is a huge singleplayer mod for Deus Ex based on the gaming community, finally released after 7 years of development.
Amazing voice acting. Brilliantly implemented humour. Intriguing story. Incredible gameplay (and level design) true to the parent game (Deus Ex). Over 20 hours of awesome content. Incredible music. Incredible replay value (mutually exclusive choices in the game).
Enough said.