Re
Captain America: The ultimate American comic book hero.
Samwise Gamgee: If it weren't for Sam, Frodo wouldn't have made it. He carried Frodo, literally.
Eowyn of the Rohirrim: The battle on the Pelennor fields would have gone differently if not for Eowyn.
Sir Launcelot du Lake: The greatest fictional warrior ever.
I hope we weren't talking about real life. There are way too many to name in real life, and I wouldn't even know where to begin.