Entire Master & Commander series by Patrick O'Brian. Have read them all at least twice, some thrice.
Lord of the Rings Trilogy
Dune Trilogy
Several John LeCarre cold war spy novels. The George Smiley ones including Tinker, Tailor, Soldier, Spy. (loved the BBC mini series. hated the movie). First Smiley novella, Call for the Dead, at least three times. Lost interest in LeCarre after the Wall fell.
Big Sleep, Raymond Chandler
The Roman Revolution, Sir Ronald Syme. twice fully re-read, and referenced hundred of times. First copy fell apart.
A Tale of Two Cities, Dickens.
Pride and Prejudice, Jane Austin (love the dialogue)
A Confederacy of Dunces. John Kennedy O'Toole
Riki Tiki Tavi and Jungle Book, Kipling. Heck, I think I read them twice before I was 12. My parents probably read them to me three or four times as a child before I could read them myself. Wind & the Willows, Kenneth Grahame, same thing but I haven't re-read it as an adult. Might do it. Man, I loved it as a child.
Illiad and Odyssey, Homer - different translations. One in older English and one in modern American.
OMG. how did I leave off Wodehouse? Thanks Fang.