Is there a more iconic image than Edward Weston's Pepper? It's almost too famous to want to include in this list but Weston is the architypal photographer's photographer. His day books give insite into the mind of the photographer, warts and all. His work still remains modern just try to overlook the vanity and pomposity of the photographer himself.
The Son of Man, Rene Magritte -- self-portrait with the hope of conveying important messages about the individual. Magritte stated “Everything we see hides another thing. We always want to see what is hidden by what we see. There is an interest in that which is hidden and which the visible does not show us. This interest can take the form of a quite intense feeling, a sort of conflict, one might say, between the visible that is hidden and the visible that is present.”