It's hard for me to say "shaped" really, but maybe calling these albums "momentous" might be more accurate.

These two were the first true metal albums I heard and I heard them back-to-back, very loud. I was a metalhead from that point onward.
Dokken "Tooth and Nail"
Metallica "Ride the Lightning"

This one defines what an album should be for me. It's the only one in my collection that I really have to listen to from beginning to end.
Queensryche "Operation: Mindcrime"

This one opened the world of the blues to me.
Stevie Ray Vaughan and Double Trouble "Couldn't Stand the Weather"

It's kind of dopey to have a greatest hits album in here, but this one got me at the right time. I got interested in Queen from hearing "Another One Bites the Dust" on the radio. While on vacation in 8th grade I bought this album and really opened up a new world for me. All the different styles of music with great guitar and bass work to boot (John Deacon is a vastly underrated bass player, IMO). Since then I've gone back and purchased several of their older albums. I must say, though, that most of their work after the greatest hits album really doesn't appeal to me very much (with some exceptions like "I Want It All" and "Hammer to Fall").
Queen "Greatest Hits"