I use scarlet runner as a snap, but it needs to be picked when young and small. Wonderful flavor, but doesn't produce well in the heat (more of a fall crop for me).

Runner beans are commonly used as snap bean in cooler climes, particularly in the UK. They don't set pods well in the heat.

Both the Black and Red Valentines make superlative snap beans.

The Black Valentine produces a bush about 24" high, loaded with straight, stringless green pods about 6" long. If they get away from you, don't worry. It's also a pretty good dry bean.