Yes, in Fallout 3 there is a man who wanders near Tenpenny Tower selling a Mister Gutsy. You must have neutral karma to purchase him however.
He's called Sergeant RL-3, costs 1000 caps, has a flamethrower for close combat and a plasma gun for ranged. He has a "Storage Module" and is able to carry things much like any other follower. At the moment, I have Charon and Sergeant RL-3 together, meaning an inventory weight of around 600 pounds.