Rationalist
Hail Voltaire
the possibility of god not existing is so close to 100%, that for all intents and purposes it's not erroneous to just simply say god does not exist in the definitive sense. Just like we say santa claus does not exist. For all you know he's real and when you become an adult he casts a magic delusion on you into thinking that you actually bought presents for your kids.
There are an infinite amount of possibilities that are non-falsifiable, and the correct, logical, and rational default stance is to not believe in things unless provided with some form of evidence. Otherwise you're just being an intellectual pussy too afraid to say no.
If evidence in favor of design could be provided, would you admit to the possibility that God exists? There are patterns in the universe which, although falling short of proving God's existence, are indicative of design. The problem with explicit atheism is that it begins with the assumption that God cannot exist.