So many to choose from. One that comes to mind is years ago playing my first ever links round at Portmarnock and topping my drive thus yielding a low dribbler into the adjacent parking lot with several people watching.
The worst shot I ever saw though was hit by my dad, who was a terrible golfer. He was teeing off on a long Par 4. I had already hit and had moved to the side of the tee box about ten yards away so that his back was facing directly at me as he hit. Somehow, almost defying the laws of physics, he hit the ball straight between his legs at a 90 degree angle to where he was aiming, where it proceeded to hit me right in the middle of my chest. There was one nanosecond where my brain was going,"Holy S&*! I just got hit by a golf shot", but fortunately the thing was only travelling at about 10 miles an hour and fell harmlessly to the ground next tome. There were then a few moments of silence before we both broke down laughing.
My worst shot ever was in a tournament, in front of a large group of people on the first tee. I was going through my pre shot routine, and on my practice swing I grazed the ball and knocked it off the tee about 5 feet. I have never seen that before or ever heard of anyone doing it either. I then proceeded to take out my 4 wood and nut it about 240 down middle.
Too many to list, but I actually once hit an iron off the hosel so badly it went 90 degrees sideways. I can't unsee that shot and it was over 30 years ago.