Billy Casper vs. Arnold Palmer (1966)
Up seven strokes on Casper, his playing partner, with nine holes to go, Palmer could have played pitch-and-putt the rest of the way and still won the '66 Open at the Olympic Club in San Francisco. Instead, the King morphed into golf's greatest Dunce. Despite his comfortable lead, Palmer started playing aggressively, hoping to break the Open scoring record held by Ben Hogan. On the par-3 15th hole, he aimed for the pin rather than the middle of the green and wound up in the sand. Palmer bogeyed and Casper birdied, cutting the lead to three strokes. Casper, sensing an opening, tied Palmer two holes later, and trounced him by four strokes in the 18-hole playoff. Sports Illustrated called Palmer's collapse "one of the great debacles of modern times, comparable to the Italian retreat at Caporetto, the Edsel car and Liz Taylor's Cleopatra." The King never won another major.