My Dad used to always be playing Marty Robbins cowboy songs. The main one was Big Iron or Big Iron (on his hip) referring to the cowboy's gun. That one is probably one of his most famous - even in UK.
I've gone for this song called El Paso. The song is a great little ballad about an outlaw who falls foul of the law because of a wickedly beautiful Mexican lady. Marty Robbins brings it alive and the memory of my Dad in the 1960s.