I'm a big Marciano fan myself but you can see how tired he got in his fights. Just like Harry Greb (I think that's the guy) kept throwing them no matter what. If he was dizzy, tired or couldn't see, he still kept coming right back at them. He always had the extra gas to go the extra mile. If anybody's interested on what Marciano's own thoughts on what it takes to be number 1, check this link out. http://www.bobdelmonteque.com/pages/rocky.htm It's a rare artical.

Anyways I agree with most of the names mentioned, but I'm surprised that nobody has mentioned Julio Cesar Chavez, that guy was a very dedicated athlete as much so as guys like Marvelous Marvin, and Bernard Hopkins. You gotta agree with me on that, he trained his ass off and left nothing on the table.