Sonic Youth - Daydream Nation.
Plenty of albums I like better (hell, even SY albums), and I rarely listen to this anymore, but honestly this may end up being the most important album in my life for hitting when I was the right age to appreciate, clearing cobwebs and setting a stage for the future. Plus always thought the term/genre "Artcore" was pretty badass. Strangely, I think The Pixies (no slouch) narrative has overwritten some of the Sonic Youth ripples.