Superconductors.
The basic concept of a superconductor is that it is capable of sustaining an electrical current without resistance. Resistance in a circuit is what causes a loss of energy, so superconductors are the closest thing we have to perpetual motion. However, they only work at near absolute zero, or more specifically, anything colder than 91 Kelvin.
When a superconductor is cooled to these temperatures, any interaction with a magnet causes a repulsion, this effect is called the Meissner Effect. The induced field in the superconductor opposes the applied field of the magnet, therefore repelling each other. So if the two repel, how is it possible to achieve any levitation? When the magnet is moved closer the flux trapping effect is engaged and the superconductor not only repels the magnet, but attracts it as well. The magnetic flux lines from the magnet are trapped inside the superconductor causing the magnet to be held at a fixed position. This is only possible if there are imperfections in the crystalline structure of the superconductor.
Of course, the opposite effect of levitation also occurs. When the magnet is picked up, the superconductor remains in magnetic suspension, and hovers below the magnet. Another phenomena is that the levitated magnet will freely move at a fixed distance over the superconductor without friction, so the applications would benefit transport, which means we can all have hover cars now.
