The Clash - London Calling and The Stooges - Fun House would probably be the last 2 albums I would take off my iPod.
Some others that aren't likely to leaving soon: The Velvet Undergrounds catalogue, Television - Marquee Moon, Pixies - Doolittle and Surfer Rosa, DJ Shadow - Entroducing and any number of Bealtes, Stones, Dylan, Prince and Springsteen albums.
Must have Beatles, no bad albums that I know of. How about some Led Zeppelin too - "IV" if nothing else, but I have Led Zep I, Led Zep II, Led Zep III, Led Zep "IV" (no name), Houses of the Holy & Physical Graffiti on mine.
Cocteau Twins - Blue Bell Knoll, Treasure
Single Gun Theory - All
Frank - Sinatra Reprise
The Pretenders - Pretenders
Steely Dan - Aja
Supertramp - Crime of the Century
XTC - English Settlement
Zero 7 - Destiny
The Beatles--Beatles 1
Elv1s--30 #1 Hits
Guns 'N Roses--Appetite for Destruction
Red Hot Chili Peppers--Blood Sex Magik
Red Hot Chili Peppers--Californication
Red Hot Chili Peppers--By The Way
Green Day--International Superhits!
Dave Matthews Band--nearly every album
Jimi Hendrix--The Best of Jimi Hendrix