

Top of the list, I think, is… just some old-school D&D. Technically, probably Old-Shool Essentials or Dolmenwood, both of which are retroclones of B/X D&D.
I just got into watching Dungeon Meshi and playing Caves of Qud, both of which are just dripping with old-school D&D influence. Plus I’ve never actually ran a full dungeon or hex crawl.
Honorable mention to Burning Wheel, 16-time annual winner of My Favorite Game I’ve Never Played. :P
I love the level-0 “funnels” from Goodman Games. If I have to pick one, let’s say the classic, Sailors on the Starless Sea.
They’re easy to pitch, and really help establish a tone, especially for players who bring a lot of preconceptions from 5e.