I never much liked Dungeons & Dragons, having started in 1980 with a different game of the same fundamental type (a fantasy/medieval roleplaying game) that I much prefer named The Fantasy Trip, and then from 1986 on with it’s pseudo-successor GURPS (the Generic Universal Roleplaying System). They’re the same sorts of games, but with different style and logic to them. I’ve played as both player and Game Master (or Dungeon Master in D&D) since 1980, and ran a computerized online role-playing company about 1989–1991, so yes, I’m a pro, though not really at D&D itself, which I still don’t like much.
With decades of play, there is no one most memorable game experience, I don’t think, and some of the most hilarious and interesting moment either involve a lot of context and back story, or you had to be there, or at least be a gamer, to get why they were great.
Playing as a game master in a game where I create and run an entire fictional world is one my favorite and most interesting things I’ve done. It presents many challenges and learning opportunities, and exercises in self-control and balance and cause and effect and creativity and it (along with my interest in games in general) greatly added to my interest in many varied subjects as well.
One game I’m fond of, which went on for years with many great points, included a great unplanned side-adventure where my character snuck into a duke’s castle in response to a series events where the duke had had a tree cut down that had a magic spirit living in it, and as things turned out, I ended up catching him alone and making him drink a potion which since he didn’t know what it was ended up turning him into a rabbit (he was a coward at heart, and since he also didn’t have much willpower, it became a permanent effect), which I then smuggled out of the castle. This left the duchy without a duke, and a child in a distant kingdom got a new confused pet.