For dnd specifically:

I ran a l20 one shot. The party struggled EXTREMELY against a group of frost giants with regeneration, because they didn't bring any fire. I thought I had overturned the adventur as they struggled to light torches and throw them into the giants eyes a and stuff

Then half an hour later, the extremely min maxed rogue tried to be eaten by the boss on purpose and proceeded to gut it from the inside out in two turns.

Rpg in general the eye opening experience of playing a game that's not dnd for the first time. We played wicked ones and it was so much fun slowly learning the rules. I remember when I understood that there is no spell list and I can just do whatever, in accordance with the dm - that was so liberating and exhilarating

All the many times that I as DM gave the PCs an encounter, and they found a way around it without fighting. Those are always fun to watch and see what players come up with!