Ah, the legendary Excalibur weapons that Sir Steiner is able to wield. This knight gains use of these powerful swords by completing various tasks. You, the player, I ask one thing: are you up for this challenge?
This sword is quite simple to obtain, unlike the second one. To get this sword go to Daguerreo. There should be an old man near the library who asks for a special item, the Magical Fingertip. This item can be obtained at the Auction House in Treno, but be prepared, as it will be very expensive!!
If this item doesn't show up, make sure you've completed the auction house sidequest, or rather, sold various items from the auction to the nobles in Treno.
Take this item back to the man and he'll reward you with the Excalibur.
This weapon should only be sought out by the biggest of FFIX fans, as in order to get this sword, you'll have to get to Memoria in under 12 hours, yes, 12 hours! If you do happen to do this, though it will be no easy task, you can get this at the Terrace. It'll be in a corner to the right side.
Seeing as it is the most powerful weapon in the game, hardcore fans will want to try for this weapon.