Another potential argument:
One of the fundamental arguments is that existence had to have been created by a deity. However, this can only be dependent on a god whose existence is not bound by the concept of time; a god who has forever existed. By positing this, one is then also positing that existence has always existed. However, if existence has always existed, why is there a need for a creator god?
The 1st law is that energy cant be created/destroyed. Everything is made of energy. Therefore, it stands to reason that existence, itself, is also eternal. This could lend a valid reason to asking why it's necessary to posit a god when both believers and nonbeliever could essentially begin by saying, "Existence has always existed." However, Occam's razor would favor the nonbeliever's side, as it doesn't take the unnecessary step of adding an unneeded entity.
Bah. Enough rambling. I'm sure there's a better way to word what I've just said. Anyhow, take care.