My tastes ran from pretty much rap only in 7th / 8th grade to pretty much only metal and guitar wankery in high school. It wasn't until college that I got into much else.
Blues Brothers - Briefcase Full of Blues
Before this, I wasn't really into music. My uncle had this when we visited right before when I was (i think) starting seventh grade. During that visit I played (or asked for it to be played) so much that I received it as a gift that Christmas. I think I was so amazed that (a) this tv band was a real band, and (b) such a thing as a live album existed. (It wouldn't be until years later that realized that Paul Shaffer was the musical director for this show.)
Various Artists - Rap the Beat
This comp was (at the time) *amazing*. I just poked around on the net and found the cover and track list, and really, it's a fairly solid collection of tunes, though with a couple obvious weak points. This comp led me to more very important albums, such as...
Flat-out *amazing*, and especially so to a white kid in the boonies of Indiana. Rakim still has (to me) the best voice of any MC. (Their subsequent stuff never grabbed me like this one, though.) Oh, and please note, the gold color of the jewelry was added after the fact -- my copy of the tape had the gold offset a bit, making it obvious. When they re-released the "Platinum Edition", they left the gold color off. :)
Beastie Boys - Paul's Boutique
The MCs are excellent, really, but Matt Dike & The Dust Brothers FTW, seriously. Oh, and if you haven't read the 33 1/3 book about this album then run-don't-walk to the store and get it. NOW.
Tone-Loc - Loc'ed After Dark
This record is one that may seem like it would be embarrassing, but actually, it's a serious piece of work. Aside from the two hits (which I actually still enjoy, believe it or not), "On Fire", "Don't Get Close", and the title track were all stellar. Again, Matt Dike & The Dust Brothers FTW. Oh, and "Cheeba Cheeba" is one of the few songs about weed that I actually love (and it featured future very-temporary Chili Pepper guitarist Arik Marshall).
Still love it. This is one of only two releases (along with Ministry's "With Sympathy") that I still own on cd, cassette, and vinyl. Check the title track, man. And like, every instrumental. And the rest, really. Don't hate it because of the hits.
Those last three are inseparable in my head, and frankly represent the last material by Dr. Dre that I like. Sorry... well, not really. Anyway, I'm not sure I need to say much about these, except that my favorite NWA track is actually the last track on the DOC record, "Grand Finale". And if you don't know who everyone is on the NWA cover, get learnin'.
Alongside rap, I was (and am) a big Weird Al fan. This represents a key record for me, and one I went back to very often. His records were my introduction to humor in music, and would help lay the groundwork for my later Zappa obsession.
Guns 'n Roses - Appetite for Destruction
Now we shift into the metal portion of the list. I wanted to play guitar as soon as I heard my cousin Tim play the riff from "Sweet Child O' Mine"... I didn't think well-known music was something that the average person could play; it brought music down to an achievable level. Thanks, Tim.
The next thing I learned was the opening riff from "One". This is still my favorite Metallica record, even though it sounds better with bass added. (Can we get a remaster on this one, pretty please? Just not by Bob Rock. Rick Rubin, maybe.)
This (along with ...Justice) is the most "prog" I think I ever got (before I got into *actual* prog years later). I love it despite the high cheese factor in the lyrics & vocals. This was the debut of the best Megadeth lineup, period.
Wrathchild America - 3D
This one's kind of a weird one, in that it's maybe the most obscure material on this list. And now that I think about it, this one has to go along with ...Justice and Rust in Peace as far as prog goes; these songs have *parts*, and time sig changes, and... yeah, you get it. Recommended if you like those other two I just mentioned.
I started playing guitar, buying guitar magazines, and realized that there was an ocean of ridiculously proficient guitar players out there, ones that would take out of my reach what my cousin Tim had previously made seem attainable. Vai was one of the few (along with Satriani) who I thought made good, listenable records that were technically so far up in the clouds.