My vote goes to the USFA single actions. These guns were very well fitted, good shooters, and hansdome to look at. They were all steel, deeply blued and beautifully color case hardened. They sere only so-so in sales, due to rather high price, but now are discontinued.
All the American made single actions from the 'Sixties are becoming somewhat of collector's items, but these were not so finely fitted and finished as the USFA guns.
And, in my opinion, guns with plastics and alloys just won't carry the charisma that all steel/walnut guns carry.
Another consideration is its "old West" look, which along with a WW II connection or roarin' 'Twenties appearance, goes a long way towards collector's wants.
That's my two cents.