My choice would be between Marc Riboud, Manuel Alvarez Bravo and Ernst Haas, who did some absolutely amazing abstracts.. All so different in style, but each with a unique touch..
http://www.marcriboud.com/
http://www.manuelalvarezbravo.org/
http://www.ernst-haas.com/
http://www.marcriboud.com/
http://www.manuelalvarezbravo.org/
http://www.ernst-haas.com/
Wynn Bullock, beyond any doubt
http://www.wynnbullockphotography.com/index.html
http://www.wynnbullockphotography.com/index.html