Hiro is given an old, rusty sword that he is told is the great Dragonsbane, and though it may not look it, it's still as powerful as ever. After defeating the dragon with it, he's told that it was really just an old, rusty sword, and the power was in him all along.
Hiro searches for Dragonsbane, a very old sword. It turns out that it was crafted in the bronze age. It has a little greenish oxidation on it, but it's still clearly in good condition.
Zig Zagged: Hiro finds the rusty sword in the first episode, and is convinced that it's the weapon destined to defeat the Big Bad. He lugs it around for ages trying to find someone worthy of restoring it, while some characters call him crazy and point out other, more powerful-looking weapons, and others quietly suggest that it might simply be a Magic Feather. Even after it's broken in a fight, he keeps Dreaming of Things to Come and pressing on with his personal quest. Eventually it's restored and discovered to be an Empathic Weapon that was secretly testing his faith, and on finding him worthy bestows its full power.
The sword was designed to look old and rusty to fool opponents into a false sense of security.
Exploited: An "Honest John" manufacturer of cheap swords keeps them in salt water for a month so he can pitch them as being long-neglected Ancestral Weapons going for a song.
Defied: "Even if this sword was great once, it'd be ruined by all this rust!"
Discussed: "Go for the rusty old sword. I bet it'll turn out to have awesome magical powers."
Conversed: "He has to pick the legendary Dragonsbane out of the Flaming Sword hanging in mid-air, the shining silver one on a plaque on the wall, or the rusty one sitting in the fireplace? Gee, I wonder..."
Deconstructed: Hiro recognizes the Dragonsbane and, aware of its fearsome reputation, cleans the worst of the rust off and carries it into battle. However, despite his best efforts to polish it up, the years of neglect have left it brittle and dull and a shadow of its legendary reputation.
Part of the reason the Dragonsbane is so effective is because every dragon that sees it bursts into uncontrollable laughter and can't concentrate on the battle.
Hiro fights a dragon with the rusty old Dragonsbane. He barely manages to cut the dragon with it before it breaks, and he flees the battle. Months later, the Dragon dies of tetanus from being cut with a rusty old sword.
Played For Drama: The Dragonsbane is the only weapon that stands a chance of defeating the dragon god Marduk... But it's been lost for eons, and when finally rediscovered, is in such a state of disrepair that it's practically unrecognizable.