As someone who always had a group of friends interested in battles, and numerous copies of Pokemon Stadium 2 with Transfer Paks amongst us, I've always been curious what sorts of fun, improbable, or clutch moments other people have had in various battles over the years.
A number of past memories of my own were noted in a recent issue of the Johto Times (Vol. 3 Issue 40 if anyone is interested), but I have plenty more. I'll post a few here and look forward to hearing those of others, too!
My cousin once defeated my Tyranitar with his Butterfree even though he couldn't deal any direct damage to me. His only attacking move was Psychic, but he'd already put Leech Seed on me with the last move from his previous Pokemon, and paired that with Supersonic and Sleep Powder for one of the most frustrating losses of my life. We still joke about it to this day!
I have a Dragonite that once tanked an Ice Beam from a Lapras in a battle against a friend, surviving with 5 HP. I had a few levels on her, but only a few since we were playing Poke Cup rules, so it was definitely surprising.