My list would have these. No particular order. This is only six, and plenty of other names come to mind, but none seem quite as solid in the firmament. I'm sure some other very obvious choices will be suggested that I'm forgetting about. And Ansel of course, but I have trouble seeing him fit on this list.

Walker Evans
Edward Weston
Gary Winogrand
Diane Arbus
Henri Cartier Bresson
William Eggleston