Bonus points for any non-D&D or D&D derivative systems.
My first RPG was Palladium Fantasy way back when my grognard uncle invited me to his groups table. I still don’t really grok it, but it was pretty formative of my ideas of what an RPG could be. The lack of balance and extreme existential threats as part of ordinary encounters included.
Needless to say, I haven’t found a group for this system in a looong while, eheh.
My first RPG was called “Het Oog des Meesters”, translated from the original German “Die Schwarze Auge”. It was probably pretty bad compared to AD&D but I loved it as a kid. In the one hand I’d love to play it again. On the other hand, playing might ruin my memory of the game. Like rewatching a bad cartoon from your childhood.