The first tape I remember buying for myself was AC/DC Back in Black.
In high school, I was into Led Zeppelin and the classic rock scene, but also into Motley Crue and Ratt...the hair bands.
Early 20's? Metallica, Soundgarden, White Zombie..things of that nature.
Now...hard to say really...I still like the things I liked before plus some of the newer bands like Disturbed and Audioslave.