A bastardized version of the old adventure that, I believe, came with one of the first editions of D&D. You know, the one where four 13-year-old boys at summer camp make characters who wind up trying to have sex with a carrion crawler and get paralyzed forever. The end.
2) First RPG Gamemastered
D&D 3.0. Junior year in high school, my game's DM was all, "I don't want to run this game anymore." Everyone else went "Not it."
For my first session, I prepped this whole thing where this lady wanted to hire the PCs but first she wanted them to go through a gauntlet of tests. And the PCs were like, no, we're bailing on this, that sounds dumb. So it was a very early introduction to player agency and improv!
Man. My parents bought me the D&D 3.0 books as a gift in like 2000. I bought a GURPS splatbook for a friend as a birthday present in... 2003.
I think the first game I bought for myself was Sorcerer, the Ron Edwards one. Senior year of college, 2006, hanging around The Source; it was just sitting there on a shelf. I'd always been into demons, and the book itself had such a confrontational tone, it was hard to resist.
That book sat on my shelf unplayed until I lost it in like 2009, 2010. I re-purchased the Annotated PDF in 2013, and ran my first game of it last August. It was everything I could possibly have hoped for--it did more, honestly, than I realized RPGs were capable of in 2006.