According to Stephen King's Dark Tower series, that would be Roland Deschain of Gilead, affectionately known as "old long tall and ugly", by his friend Eddie Dean of New York.
According to this node, a gunslinger was a freelance killer in the old American West. How such a low life became the noble knight of Stephen King's tale is just a continuation of the process by which the dirty, often illiterate laborer known as the cowboy became a dashing character in American history.
Roland is the last of a breed of men who acted as law enforcers in a world that looks a bit like the one in A Canticle for Leibowitz. However, they were not just cops, they were (sort of ) knights as well, or such was the impression I got from the books. Experts in all sorts of weaponry, their most distinctive weapons were big revolvers. I have never seen, much less handled a revolver but I imagine the famous Colts or Smith & Wessons of cowboy movies would fit the description perfectly.…