Master Chief John-117 is a character from Halo

1. Master Chief John-117 is a character from Halo. Originally named John and born in 2511, he first lived with his family on the human colony planet Eridanus II. In 2517, John and seventy-four other children his age are covertly taken from their homes and replaced with flash clones to hide the kidnapping. The original children are brought to planet Reach, one of the UNSC's headquarters, to begin intense physical and psychological training to become SPARTAN-II supersoldiers. They are assigned new identification numbers instead of last names; John becomes known as John-117.
http://en.wikipedia.org/wiki/Master_Chief_%28Halo%29