Winner's Proof

The Winner's Proof Keyblade is acquired after finding and fulfilling the tasks of the Organization XIII Mushrooms, the thirteen Mushroom Heartless scattered around the worlds in Kingdom Hearts II: Final Mix. This keyblade, along with the Two Across Keyblade, is a Kingdom Hearts II: Final Mix exclusive.

Winner's Proof's name comes from the fact that you have to surpass twelve tests (One for each Mushroom, sans the last one whose test is to surpass the other twelve's)

Winner's Proof displays exactly thirteen Mushrooms (Four in the Keychain, two in the handle and the remaining 7 on the blade, with one being the "sharp point" of the Keyblade)