This is a metal ball. It levitates. In midair. You can move it around however you want and then let go of it, and it'll just stick there, defying both gravity and common sense. The MIT Media Lab has worked this into an interface that lets both you and a computer communicate through the manipulation of physical objects. Flying objects!
As with most things magical, this antigravity ball isn't really powered by magic, but by science instead. Powerful magnetic fields controlled by a computer coupled to an optical tracking system and a projector are used to move the ball around (or hold it in place in midair) and to provide an interactive volume for the user to frolic in.
Jinha Lee at the MIT Media Lab's Center for Bits and Atoms came up with the idea (called ZeroN), and watching it in action is just a little bit surreal:
ZeroN can remember how it has been moved. Physical motions of people can be collected in this medium to preserve and play them back indefinitely. When the users move release the ZeroN, it continues to float and starts to move along the same path. This allows a unique, tangible record of a user's physical presence and motion which will continue to exist even after the death of the person.
That wouldn't be my first choice for how to go about using this thing, but then, I'm having trouble getting past how much potential there is for something like gaming. After all, gaming is all about projecting yourself into a virtual world, and the more you can physically do that, the better. It's why Kinect has been such a success, but adding an interactive physical object that floats in midair would open up tons of new possibilities, especially for training wannabe Jedi knights.