I have two very memorable ones among many of my mare. The first was before I owned her when she was with her original owner/(I'm assuming breeder). About 6 miles away from where she was there was a stud who was kept in a stallion proof fence, watched constantly and there was also a field filled with barbed wire in between his paddock and the rest of the mileage to my girl. One day, in fashion, my mare plowed - not jumped - through the fence, jumped the barb wire and busted the stallion proof fencing in half (it wasn't mare proof lol). She had a midnight rendezvous with the stud...... three different times. By the third foal she was sold with the infamy of "the red beast": stud owners beware, a record she still holds to this day
The second was when us kids decided to have little 'races' at the old barn. Keep in mind it had a 1/4 of a mile track and I have a QH who is very good at being competitive when she wants to. We took off at a nice canter until my girl decided to kick it up a notch and began to gallop. Being the not so smart kid that I was I just hung on for the ride and while I won my race, I failed to see the fact that she was bound and determined to become a cross country horse. She jumped the country jumps that were set up in the inside of the track, plowed through another small jump and then propelled me and her right into a pond. I'm positive she did this out of spite because I accidentally let my legs touch her sides gently to ask her to run. She did have a smirk on her face when we were soaking wet and drip drying.
I do have to admit though, whenever I'd lose my balance or something that ride she'd always slow down and adjust her body to catch mine!