I remember Kali Meehan being a gentleman after losing to Lamon Brewster. Considering the fact that he should have won the fight and had every right to be upset, he was pretty gracious and didn't question the scoring. On the contrary, he had this "just happy to be here" attitude and Don King rewarded him with the Rahman eliminator fight.
Tyson actually springs to mind. No matter how much you hate him, he loved the sport and always worshipped it!