For the sake of ease, I'll allow super important GameFAQs pages in this thread as well.
For some people, especially of a certain generation, I'm sure game guides were considered - if not heretical to the entire concept of gaming - a form of cheating, but I feel like a lot of kids in the 90s were indoctrinated into guide culture via the early days of the internet and the constant bundling of guides into pre-orders as an upsell that parents felt pressured to get lest their kid have been expecting the guide as well. And now, of course, Youtube has won. Whether you want to grow the biggest beard Arthur Morgan is capable of growing or hit Turn 3 on Laguna Seca exactly right, someone somewhere has you covered.
But game guides used to mean something, damn it, and these guides meant something to me.
The Legend of Zelda: Ocarina of Time: No lie, I'd read this thing like it was a YA novella as a kid. It was a bit of a hard guide to read when you were actually trying to get advice (and were only ten years old) because of its gimmick, but it was a cool gimmick: the entire thing was written in the past-tense and third person, rather than present and second person. Other guides have done this but the imagination that game filled you with was only enhanced, IMO, by the way the guide treated it as a real story.
Final Fantasy VIII: I rarely break games, but when I do, I do it because the guide meticulously breaks down just how certain magics are going to affect certain stats, points out all the areas littered with hidden draw points and gives you locations for all the materials needed for the endgame equipment and most obscure GFs. I also liked the character profiles, if I remember correctly.
Final Fantasy IX: Two (actually, one) word: PlayOnline. Six more words: The Worst Strategy Guide Ever Made
Sheamon's Xenogears Perfect Works Translation: I was fifteen/sixteen when this was finished, and it was nearly my bible
The Full Throttle and The Dig User Manuals: Both contained hints for the first puzzles to get you going in the game, and I was an eight year old idiot during the time I got ahold of these games so I really needed the help. I'd then write clues for later puzzles all over the margins of those things, to the point I wish I'd kept ahold of them so I could see what I left behind and figure out if they'd still jar my memory today.