[theundeadhero]

The Atma sword is really the strongest in the game.

To clarify for any other readers:

In the Sea Shrine go to the right on the first floor and there is a staircase leading to upper levels. On the top-most floor the Slab/Rosetta stone is found. Take that to Dr. Unne in Melmond to learn Lefeinish. Go to Lefien to get the chime which lets you into the mirage tower. In the top half, known as the Sky Castle, you find the Adamant. Take that to the smith in the dwarf village and you get Excalibur.

In the water grotto there is a sword called the Excalipur. It is a very crappy knock off of the Excalibur sword found in FFV. To get it go through the Water Grotto once. You will fight Gilgamesh on the way through and only get the Gengji Gloves. After completing your first run through go through it again. The door leading to Gilgamesh will be locked. You will find him in the cave-like area off to the right of the same floor. After defeating him you will see a sword laying on the ground. The Excalipur.