When I was in high school I was playing in a tournament(I've been playing for a about a year at this point) and I hit a ball in a greenside bunker. I actually took a practice swing in it and the two guys on the other team called me out on it. I thought they were just making it up until my teammate took their side. It was so embarrassing. I don't know how I didn't know that you couldn't ground your club in a bunker, and how our golf coach didn't tell us that(I guess he just assumed everybody knew). But yeah till this day it's probably my most embarrassing moment on the course.