I'll be honest--I'd never heard of this guy until I read his obituary, but it seems pretty clear that when it comes to completely changing how a particular field event is done, he's right up there with Dick Fosbury.
Parry O'Brien, way back in the 1950's, developed the shotput technique that seems commonplace today, starting with his back towards the final release point, and spinning 180 degrees to build up momentum. That manuever is actually called the O'Brien Glide.
O'Brien's ability and technique made him dominant, winning 2 Golds & 1 silver in three Olympics, and getting fourth place in his final Olympics. Also, from the linked above LA Times article:
"At his peak, O'Brien won 116 consecutive competitions. He was the first shotputter to exceed 60 feet and extended the world record from 59 feet, 3/4 inch in 1953 to 63 feet, 4 inches in 1959, raising it 16 times."
O'Brien was also ahead of his time in seeking mental advantages through what must have been considered odd alternative techniques back in the day. The LA Times article quotes a Time interview with O'Brien from 1956:
O'Brien practiced yoga, seeking to "dig deep into what you might call an inner reserve of strength," he told Time. He also psyched himself up for meets before that became a common practice among athletes. Time reported he would play tapes of his voice that reminded him to maintain his form and speed and ended with, "And beat them! Beat them all!"
All in all, sounds like a very interesting guy. Lots more of interesting stuff about him in the article.