Amen: The Awakening was a planned FPS / RPG with some stealth elements by Cavedog Entertainment. It was to be the first FPS by Cavedog and probably the gameplay would have been somehow similar to the original Deus Ex, but the project was cancelled in 2000. Amen would have told the story of a dark and grim future where the political balance and societies have crumbled and terrorists control a portion of the world. [Info from Wikipedia]
You can find an interesting preview with more details on the game at Tau Universe!