Telecanter asks us: do you remember the rules from 2e or earlier that made you go "Hunh?" the first time you read them as a kid?
I don't remember rules per se, but I remember a lot of monster and spell names. As I've mentioned before, my introduction to D&D back in '75 or '76 was via a friend who had mimeographed charts, but not the actual LBBs. My friend had learned to play from an adult who presumably had the LBBs, since some things like the layout for the monster tables turned out to be identical when I finally got the LBBs. However, we did not have monster descriptions or spell descriptions; we had to go on what we knew from myth, fantasy, and sci-fi.
A lot was still accessible, but some D&D-isms were pretty opaque. For example, the elementals were divided into three varieties, two of which were labeled "staff" and "device". I knew what elementals were, because I'd read Operation Chaos by Poul Anderson. But we didn't have magic item descriptions, so I interpreted "staff" in the sense of employees of a lord or monarch, or maybe in the service of a djinn or efreet (I knew those words...)
The spell lists, which included a few post-LBB spells, were mostly comprehensible, but I don't think I quite figured out what "polymorph" was supposed to be, even though I coukl break it down as "many forms". And Magic Mouth! Obviously, it does something to a mouth, but what? And why? Magic Missile was on the list, but at least I had that explained to me. Knock seemed like a silly spell, although it could distract a monster (what's that sound?) Dimension Door sounded to me like what I later learned was the Gate spell. A lot of stuff you'd *think* would be confusing to a 6th grader wasn't, because I read a lot of Fate Magazine and parapsychology -- so I knew what Clairvoyance did.
Clearly, it was playing that way, without actual written rules and a lot of plain old "making crap up", that lead me to love simpler, improvised gaming. Sure, I was lead astray for a while: there was a time when I thought Unearthed Arcana was mostly great, and The Fantasy Trip (and later GURPS) was appealing mainly because the rules implemented lots of variety directly, instead of "forcing" me to make it up.But eventually, I went back to the source of my love for D&D.