My own Stone Halls & Serpent Men: Extremely variant but still recognizably D&D. Definitely not for novice Referees, but I’ve used it with novice players and they were fine because they don’t know better (and the Profession system is more forgiving to novices who might “make mistakes”). When I get Delvers in Darkness done we’ll see if that’s more novice-friendly.
Swords & Wizardry Complete: Updated version of OD&D + Supplements I-III + some early Strategic Review & Dragon Magazine articles. About as close to a “final” OD&D as you can get.
White Box FMAG: Just the OD&D white box, very well cleaned up into a standalone game.
Blueholme Journeymanne Rules: Slightly variant take on the Holmes Dungeon & Dragons Basic Set. In theory this should be my favorite game ever, because Holmes is what I imprinted on first. In practice, it’s almost too accurate, there are some elements like multiple saving throw categories that I find annoying in actual OD&D, and the Blueholme doesn’t give you much guidance on acceptable races. Also there’s no setting or module as found in the actual Holmes book.