Polish website Polygamia has some details about Fallout Extreme (the site is Polish, but there's an English sidebar), a cancelled Fallout game that was briefly in development at 14 Degrees East back in 2000 (in case the 20th century signature "Extreme" in the title wasn't a tip-off). This was an Unreal-engine console game aimed at the first Xbox, and it is described as a cross between Fallout Tactics and a shooter. Why the game was cancelled shortly into development is not clear. There are further details on the story from the cancelled project on the Fallout wiki. Thanks Rock, Paper, Shotgun.