Keyblade
The keyblades are mysterious weapons that partially have a will of their own.
Acquisition
A Keyblade is said to choose its own master. This may be through love, power, or other unknown virtues.
Powers
A Keyblade can utilize magic abilities, such as Fire magic. A Keyblade can teleport itself to its master. It also acts like a homing signal to the Heartless. Another feature is that it can lock or unlock any keyhole, not only Keyholes. It is the only weapon that is capable of truly vanquishing the Heartless and Nobodies; otherwise, the Heartless will continue to exist.
Sora's Keyblade
Sora's Keyblade was given to him when his home world, Destiny Islands was destroyed by the darkness. Sora's Keyblade is the Keyblade of the Realm of Light. Its default key chain is the Kingdom Key. It is commonly referred to within the game as "the Keyblade". Sora's key can seal Keyholes. It is yet to be revealed if any other Keyblades have this power. The Keyblade also refuses to let anyone but Sora use it, and instantly returns to his hand when taken by another. Sora is also able to summon it back to him, as seen during his fight against Roxas. This Keyblade's original chosen one was meant to be Riku, but after Riku gave in to the darkness during the attack on Destiny Islands, it chose Sora instead. The Keyblade did return to Riku for a short time, as he was the intended wielder, but it returned to Sora after Sora showed his heart was stronger than Riku's.
Roxas, being Sora's Nobody, also has the ability to use the Keyblade, and utilizes the Oathkeeper and the Oblivion Keyblades, which earned him the name "Key of Destiny" from his fellow Organization members.
Mickey’s Keyblade
King Mickey’s Keyblade is of the realm of darkness and is shown as an inverted version of the Kingdom Key.
Riku's Keyblade
Riku's Keyblade is the Way to the Dawn. It seems to be an evolved Soul Eater, but not much is clear about this Keyblade. How Riku received this Keyblade is unknown, as he had the Soul Eater in the Land of Dragons, but he had it while in the form of Xehanort's Heartless in the World that Never Was.
Kairi's Keyblade
Kairi's Keyblade was given to her by Riku in The World That Never Was. Tetsuya Nomura has said the scene in which Riku her Keyblade hints at something.
Dark Keyblade
The "dark" Keyblade was a nameless Keyblade made out six of the hearts of the Princesses of Heart. It had the power to unlock peoples hearts and was used by Riku when he was possessed by Xehanort's Heartless. It disappeared when Sora stabbed himself with it to free Kairi's heart.
