I would also strongly recommend A Confedeacy of Dunces.
This year I have read Mountains Beyond Mountains. Rudy Rucker's Mathematicians In Love (and started Frek and the Elixer, but got waylaid by my 14-year-old's summer reading list, which I will talk about in a minute,) and throughout the winter I got caught up in a John D McDonald fest, focusing on the Travis McGee novels.
When Vonnegut died, I went back and re-read Slapstick and Slaughterhouse Five.
My favorite books of all time are probably Catch-22, A Prayer For Owen Meany, Slaughterhouse 5, a collection of Raymond Carver short stories whose name doesn't come to me, and Raymond Smullyan's To Mock a Mockingbird. I will remember others as soon as I hit the send button.
Like I said, I decided to read my son's summer reading list (he's in Honors English at the high school sophomore level.) So far I have finished Ayn Rand's Anthem (yes, she's a fascist,) Kennedy's Profiles in Courage (more interesting than I remembered,) The Iliad (tougher to force myself to read than I remember,) Sophie's World, which I haven't started, and can't remember the author.
After that, I have agreed to give War and Peace another try; I have failed at that task twice before. I am also interested in getting back into some Philip K Dick, now that many of his concerns about privacy and individualism are increasingly hot topics.
I probably left out my favorite book; it'll come to me.