Solid Snake
In "Metal Gear Solid", Otacon, an ArmsTech employee who designed Metal Gear REX, becomes a close ally of Solid Snake upon learning of REX's nuclear strike capabilities. After the events of "Metal Gear Solid", he helped Solid Snake form Philanthropy, a group whose main objective is to prevent proliferation of Metal Gear-type weapons. Snake and Otacon infiltrate the military installations and facilities of the world, delving into their compounds through stealth and cyber hacking. In a sense, Snake is the brawn and Otacon is the brains behind "Philanthropy."