Entrepreneurs get used to hearing no a lot, so by the time most of them appear on Shark Tank they've had plenty of practice. And if they hear it from all four Sharks, most of them take it without putting up much of a fight, calm in the conviction that their brilliant product or service is certain to find the right investor somewhere else.

Few, however, respond in a way that not only leaves the Sharks stunned, but turns a no into a yes, as Joe Wilcox of Sway Motorsports did in Friday's Season Six finale.

His pitch was for a compact, all-electric, three-wheel motorcycle he described as "perfect for the urban commuter." Easily controlled by a mechanical tilt mechanism under the driver's feet, the Sway rides on snow and ice, doesn't need a special motorcycle permit to drive, and is easily balanced.

A model with a top speed of 55 mph and a range of 40 miles sells for $7,999, and Wilcox said he has lined up pre-sales of $150,000, and can bring the Sway to market in a year. The toy inventor estimated that he's invested $100,000 to $200,000 in development, and has a patent on the mechanism. He was seeking $300,000 for 10 percent of the company.

Kevin "Mr. Wonderful" O'Leary was dubious, despite an impressive video showing the Sway on the street. The market for commuting alternatives is crowded, he said, and he would want to see if Wilcox succeeds in lining up distributors and manufacturers.

Guest Shark and GoPro inventor Nick Woodman was also unconvinced. "It looks intimidating to someone who isn't going to ride a motorcycle," Woodman said, and it will be difficult to get those consumers to say, "A-ha, that thing is for me."

Worried about parts, service, and maintenance, Daymond John likewise passed on investing.

That left one Shark standing when Mark Cuban said, "It's either a grand slam or it's nothing. I love it."

But then he's out, because he couldn't bring anything other than money to the business, a sentiment similar to that expressed by Lori Greiner. Then the Sharks started making their usual good-bye and good-luck noises.

"Continue to do what you're doing and find the right people and organization to build it," said Woodman. Cuban invited Wilcox to come back when the product is at the next level, and Woodman added, "We all think you're going to be successful."

And then the toymaker and inventor said four magic words. Calmly and cheerfully, he asked: "So why not invest?"

The Sharks were shocked at having their own praise turned against their decision to turn down investing. For a moment, no one spoke, until Cuban blurted out, "Make me an offer."

"We can go $300,000 for 20 percent," Wilcox said.

Cuban: "Done."

An astonished Daymond John told Wilcox, "I've never seen anyone give themselves mouth-to-mouth resuscitation the way you just did."

Cuban shook hands with Wilcox, and the guy who stopped him dead with four words walked off, clicking his heels. "I thought," he told the camera backstage, "they were going to pull the plug on me."

Brian O'Connor is author of the forthcoming book, Everything I Needed to Know About Business I Learned From Shark Tank (An Unofficial Guide), coming this fall from Riverdale Avenue Books.