Fallout's had an interesting journey as a series—starting out as one of those crunchy computer CRPGs under the stewardship of Interplay Entertainment, it was then brought under the Bethesda umbrella in 2007, turning into the FPS RPG you either love or loathe depending on which games you've played, and how traditionalist your tastes are.
Turns out, though, there's a dark horse sandwiched in between those two halves of the series' history. Fallout Tactics: Brotherhood of Steel was released in 2001, between Fallout 2 (1998) and Fallout 3 (2008).
It was developed by Micro Forté under publishers 14 Degrees East and Bethesda Softworks, and it was, at the time, kinda controversial for die-hards.
It wasn't really an RPG, and more of an RTS-style XCOM thing. Turning away from the previous games' turn-based combat, Fallout Tactics instead saw you hopping between missions and Brotherhood Bunkers—there was a turn-based option, but after doing some digging, I can't really find a single person who says that it really worked out.
While Fallout Tactics was a little before my time, the feeling I get just listening to people talk about it, in essence, a mechanically messy game that didn't quite thread the needles it needed to thread.