There are many swords of power in the Legend of Zelda series, You've got the iconic Master Sword, carried by Link in nearly every game. The Phantom Sword from Phantom Hourglass that allows you to not only harm the final boss but allows you to kill those annoying Phantoms that roam the Temple of the Ocean King. The Lomoko Sword in Spirit Tracks that does something. (I haven't played ST yet so I don't know what it does.) The Four Sword that splits Link into 4 copies of himself. There are many more swords of legend in these games. Which one is your favorite?
Master sword is a good one, as I haven't played any of the other games with other "legendary swords" (Does the fairy sword from MM count?). Though, if I had the choice of nonlegendary swords, I'd go with the Biggeron's sword from OoT.