Light

Light is the eternal force that, along with darkness, makes up the Kingdom Hearts universe. It's commonly associated with good because of its supposed nonviolent nature, though this is not true. Sora's Keyblade represents Light. This is not to be confused with Roxas' element, which is simply a basis of his powers and isn't actually categorized as any specific element. Mickey's Kingdom Key also represents light but in a somewhat different form than that of Sora's, seeing as how the four keyblade masters are representative of different aspects of light and dark. Mickey's represents the dusk, while Sora's represents day. This in turn is different than that of Riku's and Xehanort's keyblades which represent darkness. Light and darkness reside in the real Kingdom hearts, as you can tell by "Ansem" and Organization 13 using it for darkness and Sora using it to seal the Door to Darkness. Sora receives the Keyblade because, while Riku's heart becomes tainted by Darkness, Sora's heart remains pure.

Although Light is wielded by the protagonists for the most part, it is not entirely benevolent - Xemnas is able to wield Light energies in the final battle of Kingdom Hearts II. The reason for this is unknown, although, since Xemnas was able to wield all the powers of the other Organization XIII members, it is possible that he gained this ability through Roxas.