For me, that would be a long list, including "Catch-22," "Moby Dick," "Remembrance of Things Past," "War and Peace" and anything by a Bronte. I've also been neglegent in visiting with Rushdie, Dostoyevsky, Mailer and many, many others.
On the more popular front, I just scanned the New York Times hardcover fiction best seller list and found that I've read none of the authors in the top 15.
The reality is, even compulsive readers have major gaps.
So, fess up, what books are you ashamed to admit you never read.