Who was Johnny Cash?

But I will put in my guess of
Who was Clark Jones?

Before I picked my guess, I narrowed it down to my answer, your's and argosy's.

I wrote an ambiguous sentence, hence the confusion. I meant the word "one" to refer back to the word "anagram", not to the word "gunman". The answer I was looking for was Dick Cavett.

Bob's explanation:
Anagram "Live long, gunman" is "Van Lingle Mungo" which leads you to Dave Frishberg.

Dave Frishberg did some music for "The Funny Side". One of the regulars on the show was Burt Mustin, who on often played old guys in
Westerns. The show was hosted by Gene Kelly (argosy's guess) and directed by Clark Jones (my guess).

Alex, I'll take 6th degree quotes for 200. (BTW, I was actually on Jeopardy. This is MUCH harder.)

I interpreted the clue the same way everyone else did, but I'm a bit chagrined that I couldn't at least figure out the anagram - I had been using "VanLingleMungo" as my password on baseballtoaster! (I have changed it so I could post this, of course).