Joseph Heller's Catch-22 is one of the finest (and funniest) novels of the 20th century, and it's a book you must simply read if you haven't. Yossarian, the main character, also expresses some epic anti-theism... and I thought I'd create one of those quote-y picture-y things with his sentiments. So, I present:
Full quote is here.
On a slightly more serious note, the problem of evil of course remains a powerful argument against the existence of a personal, loving, God. Despite centuries of theodicy idiocy, no one has yet successful answered Epicurus' simple query.