Poisonwood Bible by Barbara Kingsolver is my ultimate favorite.
Heart of Darkness by Joseph Conrad
One Hundred Years of Solitude by Gabriel Garcia Marquez (tied for second)
The Awakening by Kate Chopin
Their Eyes Were Watching God - Zora Neale Hurston (I liked it even before Oprah made it into a movie
I'm reading Anna Karenina right now, and I think I'm going to read Love in the Time of Cholera after I finish Anna Karenina (if I ever finish it... lol).