Giants and other large races make excellent bodyguards, serving all manner of masters. They excel in this career not because of any altruistic tendencies or protective instinct, but because of their sheer size and tendency toward blind loyalty. Bodyguards have a fanatical devotion to their masters, and will often fling themselves blindly into harm's way without thinking twice.
This is a Prestige Class for Warriors, and they retain the original class's Prime Requisite, in this case, strength. Bodyguards often become Berserkers after the death of a particularly beloved master, albeit at a higher level than a normal Warrior. They can become Paladins earlier than warriors can.