Around the Dallas/Fort Worth area, Bridgeport (KXBP) always has outstanding avgas prices--most pilots in the Fort Worth area make the 24 nm trip there to fill up/top off. It is an non-towered field outside the bravo airspace of DFW and has a very nice, new and comfortable FBO that is open 24 hours a day. I've landed there all hours of the day and never had it closed. Coke machine out front, but no vending. There is a courtesy car for use--just follow the instructions by the telephone inside to gain access to it.
Another favorite FBO is just south of the Red River in north Texas, and that is Gainesville (KGLE). Also a non-towered field, they have very good fuel prices, several courtesy cars for loan and a superb facility and plenty of ramp parking. I've never had anything but positive when we've trotted the Doberman through there.