http://www.thedarkmod.com/The Dark Mod is single-player a total conversion mod for Doom 3 inspired by the Looking Glass Studios stealth games Thief: The Dark Project and Thief 2: The Metal Age. It's designed to mimic the gameplay of those games as well as feature a number improvements to the design.
If you liked the first two Thief games you owe it to yourself to play this, as The Dark Mod probably the closest thing to a modern equivalent of the earlier Thief series there is.
Some missions I recommend:
-Knighton Manor
-Tears of St. Lucia
-Return to the City
-Glenham Tower
-William Steele: In The North (difficult)
-A Score to Settle (difficult)
-The Heart of Lone Salvation (difficult)
Some missions recommended for beginners are The Crown of Penitence, The Outpost, The Parcel, and Too Late. I suggest playing at least one of those missions first even if you've played the original Thief games, as The Dark Mod is often considerably more difficult than Thief.
Trailer:
http://www.youtube.com/watch?v=x3v1YupBC3Y&hd=1A Let's Play of "William Steele: In The North" I recorded recently:
http://www.youtube.com/watch?v=Zf_NdVr8ulU&hd=1A video of the mission "Too Late" by someone else without narration, in case you find my voice too annoying.
:
http://www.youtube.com/watch?v=RFUnbXFvrgM&hd=1
