In no particular order (and ignoring sub-genre debates):
Nirvana - Bleach, Nevermind
Pearl Jam - Vitalogy, Ten
Soundgarden - Down On The Upside, Badmotorfinger
R.E.M. - Monster, Document, NAIHF (purely for 'Leave'), Murmur
Pink Floyd - DSOTM, WYWH, Animals
Rolling Stones - Sticky Fingers, Let It Bleed
Can - Tago Mago, Ege Bamyasi
Bruce Springsteen - Born To Run, Live 1975-1985
Velvet Underground - Loaded, White Light/White Heat
Smashing Pumpkins - MCATIS
Led Zeppelin - I, III
Neil Young - Zuma, Harvest
Neutral Milk Hotel - In The Aeroplane Over The Sea
Paul Weller - Stanley Road (not the 'cool' choice, but the production and 3/4 of the album kills anything else in his catalogue)
The Band - The Band
The Doors - The Doors
Mars Volta - Deloused In The Comatorium
David Bowie - The Man Who Sold The World, TRAFOZSATSFM
Guns 'N' Roses - Use Your Illusion II
My Morning Jacket - The Tennessee Fire
Blind Faith - Blind Faith
Jeff Buckley - Grace
Kings Of Leon - Youth & Young Manhood (before the flood of **** that followed)
Jimi Hendrix Experience - Electric Ladyland
Iggy & The Stooges - Raw Power
Radiohead - The Bends
RHCP - Blood Sugar Sex Magik
Manic Street Preachers - The Holy Bible, Gold Against The Soul, Everything Must Go
and finally... (one of the most difficult to stick in any one genre)...
Bob Dylan - (going for just his "rockier" albums for the sake of this thread) Highway 61 Revisited, Blood On The Tracks, Modern Times, Blonde On Blonde, Bringing It All Back Home