Ekalavya

When Dronacharya asked him for his right thumb as "Guru Dakshina" Ekalavya unhesitatingly cut off the thumb and gave it to Dronacharya.

There is a little known sequel to this story. Eklavya was asked whether he ever regretted the act of giving away his thumb when he was dying.

His reply was "Yes ! I regretted this only once in my life. It was when Pandavas were coming in to kill Dronacharya who was broken hearted on the false news of death of his son Ashwathama and had stopped fighting. It was then that I regretted the loss of my thumb. If the thumb was there , no one could have dared hurt my Guru"