Have Gun Will Travel was certainly one of my favs, and still wins for the "cool" factor. The name "Paladin", the horsehead logo, black outfit, etc. have always had a very high cool factor for me. Wanted Dead or Alive & Maverick may be my top 3, but I loved all the Warner Bros westerns that came in the early 60s....Cheyenne, Sugarfoot, Bronco Lane, Lawman (John Russell). Gunsmoke, Bonanza, and many others will always be classics. Which leads to the question...was there ever a really BAD western series? If so, I don't seem to recall it.
Oh yeah...The Rifleman was a favorite of mine too.