Here's my 2 cents:
Jesus
Mohammed (I'd like to listen to them debate)
Ernest Hemingway
Abraham Lincoln
Jack Johnson
John L. Sullivan
William T. Sherman
George A. Custer
Wyatt Earp
Joshua Lawrence Chamberlain
Adolf Hitler (yep, as much as I don't like him I'd like to hear what he has to say).
Malcom X
I guess that's it.