#12 Gray Fox

Gray Fox, formerly known as Null, was the codename of FOXHOUND agent Frank Jaeger. He was the only active field agent of FOXHOUND to achieve the Fox codename, FOXHOUND's highest commemoration. He was decorated five times. Fox was Solid Snake's war buddy and best friend after Operation Intrude N313, but Fox's loyalty to Big Boss, forced him to betray Snake during the Zanzibar Land Uprising. He survived his injuries during his battle with Snake and was outfitted with a powered exoskeleton and given intense gene therapy. He confronted Snake as a neutral force in Shadow Moses before dying at the hands of Liquid Snake.

Gray Fox first appears in the original Metal Gear who goes missing during a mission prior to the events of the game, his last transmission being a cryptic message simply saying "Metal Gear". Solid Snake's initial objective in the game is to rescue Gray Fox, who reveals the true nature of Metal Gear to the player.

Fox returns in Metal Gear 2, having left FOXHOUND and defected to Zanzibar Land to join Big Boss' side. Fox pilots the new Metal Gear model, Metal Gear D, and confronts Snake a few times, while secretly assisting him as an anonymous informant. Snake destroys Metal Gear D and ends up being challenged by Fox to a fistfight in the middle of a minefield.

In Metal Gear Solid, Gray Fox appears under the identity of the Cyborg Ninja, an assassin in a powered exoskeleton and armed with a high-frequency blade, who challenges Solid Snake to a fist fight, even though his ultimate goal is to help him. He also provides Snake cryptic advice via CODEC as a faceless contact named Deepthroat. Gray Fox is later killed by Liquid Snake, piloting Metal Gear REX, after Fox destroys the vehicle's radome with the use of a prototype rail gun attached to his arm.