The only time I had a shaft break on me was three years ago, in the semifinals of the club championship. Great timing. lol
Struck a solid tee shot on the 10th hole, one of the toughest driving holes on the course. The shaft snapped shortly after impact, the ball ended up in the water hazard to the right. Thankfully I was 4-up on my opponent at the time. The head pro informed me that I could replace the driver or the shaft, whichever. I raced up to my car in the parking lot and switched out the shaft.
The only other weird equipment situation I've encountered was when the face of my driver cracked. I hit what I thought was a great tee shot, but the ball went nowhere and the sound at impact was 'metallic' sounding. I look at the face and sure enough - the face had cracked. Just playing with my buddies, ended up having to play 3wood for the remainder of the round (5-6 holes). Fortunately for me the head pro at the course I was playing was a PING guy, he said to me, "I can get this replaced at n/c to you." Ten days later I get a call from him letting me know my replacement was in.
In all the years I've played, thousands of rounds, only two instances. I guess that's pretty good.