Sweden's Marcus Kinhult was lost for words after producing a brilliant finish to claim his first European Tour title in a thrilling climax to the British Masters at Hillside.
Kinhult's chances looked to have gone when he surrendered a one-shot lead with bogeys on the 15th and 16th.
Pepperell had set the clubhouse target on 15 under after a closing 66 before MacIntyre produced a stunning eagle-birdie finish to join him at the top of the leaderboard.
A four-man play-off looked on the cards when Kinhult birdied the 17th and playing partner Wallace missed from four feet.
But after Wallace also missed for birdie on the last, Kinhult holed from 12 feet to seal a remarkable win and secure the £500,000 first prize.
"I'm speechless, I don't know what happened the last two holes," Kinhult said.
"I was behind Matt and he looked really solid but I birdied 17 and all of a sudden I had a putt to win – it's incredible.
"I have never felt that pressure before. Richie (Ramsay) gave me a good read so I just tried to do the same thing and holed it.
"There's a lot going through my mind, a lot of emotions and I am just so happy that I managed to handle those pretty well. It's really special. I have been waiting for this moment for 20 years."
Kinhult, who won the prestigious Lytham Trophy as an amateur but had missed his last four cuts on the European Tour, added: "This game is so weird. It's small margins.
"My game felt okay but I just couldn't make a cut. I got off to a good start and just kept the momentum through the week."