Yusus Karsh (1908-2002) is one the most extraordinary photographers that I have come across. Primarily a portrait photographer, he has photographed a many important personalities from political figures to actors and musicians and athletes. His body of work is simply outstanding. Some of the most beautiful black and white portraits I have seen. He became famous over night when he took a portrait of Winston Churchill in 1941.
His website http://www.karsh.org is well worth visiting; My favorite section is the portraits sections where a number of his portraits are depicted and even more wonderfully each one comes with an anecdote, a remembrance of how that image was taken.
Here is another article I read which talks at length about his work, style and techniques. http://www.sciencetech.technomuses.ca/english/collection/karsh.cfm
I absolutely love his B&W images. They are what I think about when I talk about images which are timeless.
Here's another one of Mohammad Ali and the beautiful Elizabeth Taylor..
