Hmmmm.... I have a lot of memories, funny ones, sad ones, embarrassing ones, some very much not family friendly.
Kinda hard to pick just one.
I'll go with an embarrassing one. Happened when I used to skateboard.
Both my cousin and I were at the local skate park, and we were doing tricks off of a waist high ledge.
Well, we were both doing heelflips, and the thing that sucks about the heelflip, is that if your heel stays in contact with the board too long, instead of spinning like normal, it can cause the board to flip up.
Well, there was this cute girl around my age who was crushing on me hard, because when it got too hot, I would skate in a tank top or shirtless, and being a 14 year old kid, I was bulking up, so I didn't look wiry anymore.
Well, it was my turn, I heelflipped off of this ledge, and my heel stayed in contact with the board too long, causing the board to flip up, and I landed right on my you-know-whats.
Well, this was long before I learned that the best way to handle a hit to the groin if you're a dude, is look up and bounce up and down, so I was just on the ground, writhing in pain in front of the girl I liked.
She initially thought it was funny, until she noticed I wasn't getting up, and comforted me. Mind you this was summer, and she used to come to the skate park after she got done swimming.
So, I guess it wasn't totally embarrassing, getting a hug from the girl you liked in a bikini as a 14 year old was cool, but that was still my gnarliest skateboarding biff, and I've had some gnarly ones.