I once asked my father this question. If he could have a conversation with one human being from history, what would his choice be? He said "Hitler. I would want to understand how a human being can be this evil."
My own choice is Abraham Lincoln. I would be curious to see how the real man lived up to the legend that has sprung up around him. I would also be curious to see how someone can deal with two dead sons, lifelong depression, public scorn, years of a horrifying war and a lunatic wife, and still keep on functioning.
What about you?