The Sword of Wizardry is an arcane blade that channels an elemental force directly from the source plane. The surface of the blade is actually a microscopically thin planar portal through which only elemental energy can pass. The sword is attuned to the true elemental nature of the wielder, and changes depending upon who holds it. Even the runes on the hilt will reconfigure themselves when the blade changes hands.
It is both a powerful energy blade and a source of insight into one's true nature. A fire mage, for example, may find out he is truly attuned to the frost of the Gray Glaciers. A warrior of light may find himself wielding a foul smelling blade coated in viscous ichor from the Seven Cisterns of Godless Slime. This sword does not require knowledge of magic to use.
This is my (somewhat last minute) contribution to "Swords & Wizardry Appreciation Day."