The ballsiest fighter bar none is Chris Byrd. Here is a man who fought in the amateurs as a middleweight. He fought his entire career at heavyweight without a punch. Roy Jones went from starting at middleweight to heavyweight FOR 1 FIGHT, and everyone was lauding him as the greatest of all time for doing it. Yet, Chris Byrd has done it his entire career and nobody says jack about it. Imagine fighting guys that weigh anywhere from between 50 and 100 pounds more than the weight you should be fighting at FOR YOUR ENTIRE CAREER. THAT'S BALLS!!!!
I agree with Chris Byrd and I would include Barrera: Hamed, Junior Jones twice, Morales the third time after he unified, Marquez, McKinney, Juarez twice, Tapia, Ayalah, and taking a rematch with Pac.
holyfield fought everyone in the division for the last 15 plus years similiar to what ali did in his era