s/LaSH mentioned the Japanese legendary sword Masamune. What he didn't mention were the other two legendary blades, Murasame, and Muramasa.
Goro Nyudo Masamune was a real person, living in Japan around the late 13th-early 14 century. He is regarded as a swordsmith of godly proportions. The idea of a single blade bearing his name though seems to be just legend.
Murasame is the cursed blade, though its power is extreme. It is unnaturally cold supposedly, meaning that when drawn it sheds drops of water since it cools and condenses the water vapor around it. Supposedly, if you put this blade and the Masamune blade into a stream, the Masamune blade would repel leaves from itself, but the Murasame blade would simply cut them as they run into the sword.
Muramasa, like Masamune, is a historical Japanese swordsmith, though very little is known about him. He was supposedly a student of Masamune, but whereas Masamune held that a sword was meant to be used in defense, to protect life and not take it if not necessary, Muramasa believed that swords were meant only to deal death. Hence, his blades are associated much more with death and bloodshed than Masamune's (though no actual swords are, as far as I know, historically attributed to Muramasa). Like Masamune, the legends say that there is a single sword out there that bears his name; the Muramasa (sword). Though not cursed, this sword is most likely quite likely to pull its wielder into bloody conflict (that's just my assumption though).
And of course, all three swords are very popular in
Final Fantasy games (though Muramasa only appears in the most recent games).
More information can be found here:
http://www.hybridbe.com/fa_20202.shtml
