This is not a poll, but a list--not my list--everyone can put what they want. BTW, when I write "most important," what I mean is those with which an "educated" person should be familiar. Like the great books, but for just religion and philosophy.
The Tora, The Bible, The Koran. These three books have had a huge impact upon human thought and understanding. I can't remember the name of it, but the first book on "Wicca" was a book where someone invented the religion by talking about what he thought witchcraft -should- be without doing any actual research. With all the Wiccans in America, if you're an American, you should get around to reading this eventually. Metaphysics, by Aristotle. I'd really like to take a look at Neich myself.
The Republic, Plato A Treatise on Human Nature, David Hume 1662 BCP Thus Sprach Zarathustra, Nietszche Das Kapital, Marx Pensees, Pascal On Liberty, John Stuary Mill Upanishads Bhagavad Gita Being and Nothingness, Sartre Too many to name