The most unusual skate , I saw Post Modern Skateboard $ 99.95

These are the annular skates that are propelled by leaning side to side, allowing you to glide along as if riding a skateboard without pushing off the ground. Riders simply place their feet on the two platforms and lean side-to-side to rotate the rubber wheels around the feet, propelling riders forward in a serpentine motion similar to longboard skateboarding. Since the wheels are not connected, riders can easily perform 720° spins and turn on a dime, while stopping is achieved by placing toes on the ground. The wheels are 10" in diameter, allowing them to traverse short grass and dirt surfaces. The included extendable rod can be connected to both wheels, providing stability to novices and hastening the learning period. Supports up to 200 lbs. Ages 8 and up. Red or Green. Each: 10" Diam x 4" W. (5 lbs.)

http://www.hammacher.com/Product/87067