For me it is Pauls Boutique. Very personal reason why.
In my art class in high school even though she was told numerous times not to do so by other staff, my teacher would play music during class. Her room was tucked away in the side back of the building with only 2 other rooms, the band room and the calculus teachers room (It was the latter who complained about her playing music).
Any way, I was already listening to Hip Hop and believe it or not, this was pretty rare for a white kid back then, especially in a suburban town. I had grown up in a city in New Jersey (Elizabeth, right next to Newark), so I was exposed to what I considered actual Hip Hop (BDP, Big Daddy Kane, etc. etc.), not just the Beastie Boys. We then moved to the suburbs the summer before 9th grade. The town we moved to all of the kids listened to Def Leppard and hated "Crap Rap." This was 1988.
I was a skateboarding punk rocker who also already considered himself a snob on real Hip Hop. As you can imagine, or maybe not since things have changed so damn much, this did not go over well with my fellow students. I was an outcast and it was easily the most depressed I have ever been in my life.
Being one of the few white kids at the time who really listened to Hip Hop, a lot of my fellow white folks loved to call me Beastie Boy as it was all they knew of Hip Hop, and I fucking hated it. By extension, I hated the Beastie Boys.
When Paul's Botique came out, my art teacher played it non stop, and part of it was to fuck with me. She knew the other kids called me Beastie Boy, and thought it was funny I hated it so much. (She was right). So she would love to play Pauls Boutique as she knew it would get on my nerves.
Funny thing happened though. She played it so damn much I eventually began to love it and realized how damn good it actually was.
Typing this all out, life is funny, especially High School.
Anyway Check Your Head is a close runner up. No doubt.