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 Firaga magic. Sora's can lock people's hearts, along with the hearts of worlds. Riku's is able to unlock said things. A Keyblade can teleport itself to its master. It also acts like a homing signal to the Heartless.

Sora's Keyblade
Sora's Keyblade is of the realm of light and was given to him when his home world, Destiny Islands was destroyed by the darkness. Its default key chain is the Kingdom Key. It is commonly referred to within the game as "the Keyblade." Soar's key can seal Keyholes. It is yet to be revealed if any other Keyblades have this power.

Roxas has two Keyblades; being the Oblivion, the other being the Oathkeeper.

Mickey’s Keyblade
King Mickey’s Keyblade is of the realm of darkness and has an unknown origin, but is assumed to have been acquired in the realm of darkness. It 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.

It is assumed that either Maleficent or Xehanort's Heartless gave Riku the ability to wield it.

Kairi's Keyblade
Kairi's Keyblade was given to her by Riku in the World that Never Was. It is like Sora's keyblade, but with the Mysterious Abyss key chain.

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.