Fenrir

The strongest Keyblade in the game, it's even stronger than the Ultima Weapon. It can be claimed when you have done the following:
1. Defeat Sephiroth in a one on one battle (I think your teammates help you in proud mode).
2. After the battle with Sephiroth, tell Cloud his location.
3. Go tell Sephiroth that Cloud is on his way to fight him.
If you do all of the following, Tifa will give you this Keyblade. It has tremendous attack power, but isn't good at magic and lowers the number of hits in you combos. This Keyblade work well with the Ultima Weapon when your in Final Form.