Designers of a personal aircraft are selling their prototype, but you have to agree not to use it:

"NOBODY HAS has ever done anything like it," said Michael Moshier, chief executive of Trek Aerospace, the company that designed the machine. "It is the first aircraft that you can strap on your back and allows you to fly around like a bird."
He says the compact SoloTrek XFV can hover for more than two hours at a time and is easy to fly.
The machine stands about 7 feet tall (2.1 meters), weighs more than 300 pounds (136 kilograms) and is a somewhat bizarre-looking contraption with its two overhead engines above the tripod frame that holds the pilot. It can hold a pilot and gear weighing up to a total of 240 pounds (108 kilograms).
The aircraft is still in the developmental stage, but Moshier envisions a day when the sky is full of people dashing across town in the flying machines, which operate much like a helicopter.
While the public has never seen the aircraft fly because the testing has been private so far, Moshier assures potential buyers that the machine works and the company has pictures on its Web site to prove it.
"We have never demonstrated it publicly," Moshier said. "But it could (be seen in public) as soon as six months if things go well."

....The pilot flies using a pair of joysticks that control the engines on the aircraft, which made its maiden voyage in December 2001. The machine is about as loud as a leaf blower, but designers are working to make it quieter, Moshier said.
There is one hitch for the top bidder, however. The winner will not be able to fly the aircraft home and must sign an agreement promising not to operate the machine as the company does not want to get sued if somebody gets hurt using it, Moshier said.
Because of this, Moshier expects that a museum or aviation enthusiast will weigh in with a top bid that he expects will top the $1 million mark during the one-week auction, which starts Friday.
"Frankly, we need the cash," Moshier said. [Reuters]