#1 is an absolute no-brainer for me, one of the single greatest, most complete albums ever created:
DSOTM
Top 5:
Pink Floyd - Dark Side of the Moon
Black Sabbath - Sabbath Bloody Sabbath
Lynyrd Skynyrd - (Pronounced 'Lĕh-'nérd 'Skin-'nérd)
ZZ Top - Tres Hombres
Alice Cooper - Billion Dollar Babies
Honorable Mention:
Eagles - Desperado
Stevie Wonder - Innervisions
Elton John - Goodbye Yellow Brick Road
Aerosmith - S/T Debut
Blue Oyster Cult - Tyranny and Mutation
Allman Brothers - Brothers and Sisters