I don't think I've ever intentionally broken a club, but I've taken intentional actions that led to one or two broken clubs. Like slamming a three wood into the ground, which caused it break. My intention was not to break the club, like Stenson snapping one over his knee, but I also can't say I was overly concerned with the outcome. I also lightly tapped my bag once after with a three iron after a shot on the ninth at Cog #4. Found out about three holes later that I had apparently caught the driver shaft in exactly the right/wrong spot. Again, no intent, but the result was the same.
Last time I broke any club was at Broadmoor in Indianapolis before the Midwest Mashie. I hit 8 iron from about 145. The shaft broke inside the grip, which remained intact. Pretty crazy. Put the ball on the back right of green and two putts later had par, but no 8 iron for the weekend.