Atheist.

No arguments that I've heard for the existence of a deity have met their burden of proof. For some of these deities (the Abrahamic god, gods of most eastern religions, Zeus, Xenu), I actively assert they do not exist, while for others (e.g. a deistic god) I can't honestly claim they don't exist due to the lack of falsifiable claims involved, but I still don't believe claims that they do exist.