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.
Any of the crazy, mostly-single-page, mostly-free RPGs made by Grant Howitt. They start off sounding almost sensible (Death was the Only Road Out of Town, System Shutdown), then start pushing the boundaries (Honey Heist, TRAMFORCE), before going all in on the madness (Seans Bean star in: A VERY NORTHERN CHRISTMAS, Jason Statham’s Big Vacation). Great for a last minute one-shot with zero planning required and maximum laughs produced.