By Mark Trevelyan

LONDON (Reuters) - Two teenage sharks and a flying squirrel made their mark at London 2012 as outstanding new talents with their best years still ahead of them.

China's Ye Shiwen stunned the swimming world by covering the penultimate, freestyle lap of the 400 meters individual medley faster than Michael Phelps in the men's final, and her last lap quicker than Ryan Lochte in winning the male equivalent.

"I was trying my best to come from behind," said the 16-year-old, who won two gold medals and was forced to fend off doping insinuations that were unsupported by any evidence.

A year younger than Ye, Lithuania's unassuming Ruta Meilutyte seemed amazed by her victory in the 100m breaststroke.

"It came as a complete surprise when I touched. I was not looking round. I was not looking at which position I was in, whether I was last or I was first," she said.

Watched by billions, the Olympics provide the ultimate stage for any athlete and each successive Games etches new names on the world's sporting consciousness.

Some dominate a single Olympics, like U.S. swimmer Mark Spitz at Munich in 1972, while others - like Phelps, Jamaican sprinter Usain Bolt, Soviet gymnast Larisa Latynina or "Flying Finn" Paavo Nurmi - blaze a trail of victories over two or more Games.

Some, like boxing gold medalist Cassius Clay in 1960, use the Olympics as a platform for glory in a different arena. As Muhammad Ali, he became world heavyweight champion and one of the greatest sportsmen of the 20th century.

There is more at stake than sporting success.

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Sponsors are salivating over the earnings potential of athletes such as 16-year-old U.S. gymnast Gabby Douglas, nicknamed the Flying Squirrel, who won both a team gold and the all-around individual competition.

Within hours, cereal maker Kellogg Co adorned its Corn Flakes boxes with the smiling face of the first African-American to take the all-around title. Some estimate her earning power at up to $10 million over the next four-year Olympic cycle.

"The gold medal alone doesn't get you to first base in marketing. It's the persona that goes with it," said Lynn Lashbrook, a Portland, Oregon-based sports agent.

"I can't think of another person in this category: female, young, articulate, great smile, this is unique. This will be off the charts."

In the velodrome, Britain's Laura Trott emerged as the next big name in track cycling. At her first Games, she claimed two golds, in team pursuit and the six-event omnium, and at 20 was the youngest female track rider to win gold at any Olympics.

Like Douglas, she has the magic combination of a winning performance and a winning personality, and she could easily have another three Olympics to look forward to.

"Her ability as a bike racer is phenomenal already, which is quite startling. But I think it's more about her attitude, the way she approaches her life, her training, analysis of herself, of success. She's just a joy to be around," said British cycling director David Brailsford.

In athletics, the big headlines belonged to Jamaica's Bolt, for his "double treble" of 100m, 200m and 4x100m titles, and Kenya's David Rudisha for a world record-breaking run in the 800m final.

But not far behind them were athletes who laid down a marker as names to watch in the future.

Bolt's countrymen Yohan Blake and baby-faced Warren Weir, both 22, took the silver and bronze in the 200m, and 18-year-old Nijel Amos from Botswana came second behind Rudisha in the 800m to claim his country's first Olympic medal.

It could even be that a future Olympic legend may be lurking among the legions of athletes who left London empty-handed.

At the Sydney Games in 2000, a gawky-looking 15-year-old called Michael Phelps came 5th in the 200m butterfly.

Twelve years and 22 medals later - 18 golds, two silver and two bronze - the American retired as the most successful Olympic athlete of all time.

(Addtional reporting by Julien Pretot, Steve Keating, Toby Davis; Editing by Belinda Goldsmith and Matt Falloon)