Don Quixote, Cervantes - Has become a metaphor for writing/reading for me. Don Quixote goes insane and decides to exist in a fantasy world, not unlike the experience of reading and/or trying to write a book of my own. Cervantes is also hilarious, and the diversity of experiences and characters in this book is a delight.
LOTR, Tolkien - For me, there is no room on my fantasy list for anyone but Tolkien. Still enjoy other works, but I always come back to Middle Earth.
Cannery Row, Steinbeck - Love East of Eden and everything else by him, but Cannery Row is such a joyful, beautiful book that, if I had to choose just one, I would choose this one. Travels with Charley is also a great read.
Fools Crow, James Welch - Ought to be required reading for Americans, IMO. Told from the perspective of a Blackfoot native man in 1870 (Welch has Blackfoot heritage). Historical fiction and so much more.
Crime and Punishment, Dostoevsky - My introduction to Russian Lit and still one of my favorites. Came in expecting something heavy and "important," and laughed and cried throughout.
The Waves, Virginia Woolf - Reading Woolf is like having a glass of that really expensive scotch you only take out once a year because it's just too strong and too good to have too often. My favorite so far is The Waves. She's not for everyone, but her sentences are an inspiration. Would recommend starting with To The Lighthouse though.
To Live, Yu Hua - Chinese novel that follows a character through the Cultural Revolution. Incredibly beautiful and sad. Made into an excellent movie by Zhang Yimou.
So many others. I also love ancient sources like the Bible and the Iliad.