Will, my choices reflect a preference for environmental portraiture, hence Sander and Cunningham. Steichen did some wonderful portraits; Garbo comes to mind. For Cunningham, the portrait of her father at 90, and her early portrait of the painter Morris Graves, the dancer Martha Graham; all of them excellent. As noted above, the portrait series of "People of the 20th Century" by August Sander is loaded with excellent environmental portraiture.

This may be a very long thread!