About the best flavored bean I have grown/eaten, was some yellow tepary beans I got seeds for. It grows, and sets beans in really hot weather, when the regular beans won't. It grows fast and puts on a lot of dry beans, but cannot be eaten as green beans. Teparys were/are grown by just a few tribes in the desert southwest, but several more varieties are grown in Mexico. I've only eaten black, white, and yellow ones from here in AZ, but of them, and of all the other beans I've eaten, I prefer the yellow ones.
Tepary beans are available commercially, but are pretty pricey for beans, somewhere around $5/lb online. They are higher in protein than regular beans. They most likely would have been eaten by various Mountain Men traveling along the Gila and Lower Colorado Rivers.