This is a tough call. Much easier to do a top 25 or top 50. This is the stuff that has unfluenced my musical tastes the most. I know there are some I'm forgetting. In no particular order.
Hendrix: Are You Experienced?
Fleetwood Mac: Rumours
Zeppelin: II, IV, or Physical Graffiti
Stones: Sticky Fingers or Let It Bleed
ZZ Top: Tres Hombres
Who: Who's Next or Quadraphenia
Floyd: DSOTM or The Wall
Springsteen: Born to Run
Joe Cocker: Mad Dogs & Englishmen
Allman Bros: Brothers & Sisters
Hendrix: Are You Experienced?
Fleetwood Mac: Rumours
Zeppelin: II, IV, or Physical Graffiti
Stones: Sticky Fingers or Let It Bleed
ZZ Top: Tres Hombres
Who: Who's Next or Quadraphenia
Floyd: DSOTM or The Wall
Springsteen: Born to Run
Joe Cocker: Mad Dogs & Englishmen
Allman Bros: Brothers & Sisters