Development Hell: The film adaptation. Cult director Roger Avary was tapped to write and direct, then was sent to jail for vehicular manslaughter. When he got out, the funding had dried up. Supposedly he's still attached, but nobody wants to fund a video game movie in the age of comic book movies.
What Could Have Been: Originally, Wolfenstein: Enemy Territory would have been a sequel towards RTCW. Only the multiplayer portion of the game made the cut, as a free downloadable game, with the single-player portion of the game being cut. This paved the way for the Enemy Territory series which continued with Enemy Territory: Quake Wars.