He bets on football and basketball, is worth hundreds of millions of dollars, and has been so successful that many Las Vegas bookmakers are afraid to even take his bets.
Walters has been almost as elusive as Howard Hughes, avoiding publicity, reluctant to reveal his secrets.
But after 30 years of unprecedented success, the man who calls himself a Kentucky hillbilly agreed for the first time to open the door into his betting life in Las Vegas - a life he describes as one long hustle - in betting parlors, in pool rooms and on the golf course.
More people bet on the Super Bowl than any other sporting event. So, how does a professional gambler approach the big game?
Extra: The "Keyser Soze" of Las Vegas?
Extra: Billy Walters' Analytics
Extra: The $3.5 Million Bet
When Walters golfs, it's mostly for fun. He used to make his living off it. And he showed us how the hustle worked with Gene McCarlie, an old friend and casino owner.
"Who's the better golfer?" correspondent Lara Logan asked Walters and McCarlie on a golf course.
"He is," both men replied simultaneously, laughing.
"By far. Believe me," McCarlie added.
"How much money have you taken off him over the years?" Logan asked.
"When I met him, he was driving an old Cadillac full of bullet holes. Had no air conditioning. Now, he's a very wealthy man," Walters replied.
On the day we went along, the two buddies decided to play for $5,000 a hole, with a few side bets along the way.
"What's the price?" Walters asked.
"Five-to-one for birdie," McCarlie replied.
"I'll take 15," Walters countered.
"Ten," McCarlie said.
"You got it for a dime!" Walters agreed.
Walters just missed a 60-foot putt, but after only three holes, he was up $17,000. Small potatoes for Walters.
"What's the most you've ever made on a hole?" Logan asked.
"Probably $400,000," Walters said.
Asked what his biggest win was on a round of golf, Walters said, "Probably a million bucks, around a million dollars."
"That's a lot of money," Logan remarked.
"Yes. I never got to bed to with it. I lost it all in the Horseshoe Hotel playing blackjack before I went to bed," he replied.
Asked if there's anything he doesn't gamble on, Walters replied, "Not really."
He gambled on the Super Bowl last year and won $3.5 million. Nevada is the only state in the country where taking bets on individual games is legal. Most bettors come to a sports book inside the casino, to lay their bets, wagering $2.5 billion dollars every year.