A logo for the godless - the looking glass
There's been some recent discussion on what atheists should use as an icon. Something analogous to the Cross or the Star of David. It should look good as jewelry or a bumper sticker or wherever.
My suggestion? The Looking Glass.
It's iconic. It's easy to draw - the spray paint version is just a circle and a line. It has a positive rather than negative connotation. I'm thinking of the sherlock holmes metaphor - those who wield the looking glass are closely examining the evidence in the world and the universe rather than taking answers on faith and authority. They are People of Science rather than People of the Book.