hmmm....
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.