Well it's sort of a logical proposition, similar to a math equation, there can really only be one right answer and I only see two possibilities, as they're both definitive.
Just like 2+2 only has one right answer, the question of "Does God exist?" can only possibly have one right answer, too, right?
There are two positions to take, "yes, God does exist" = theist, and "no, God does not exist" = atheist. There can be no middle ground unless you decide not to take a position on said question, in that case you would be an agnostic = "I don't know if God exists"
I'm an agnostic atheist = "I don't know if God exists, but I believe God does not exist".
You could be an agnostic theist = "I don't know if God exists, but I believe God does exist".
A gnostic atheist = "I know God does not exist and I believe God does not exist".
A gnostic theist = "I know God does exist and I believe God does exist".
So it all depends on what you know and what you believe. Gnosticism deals with knowledge, atheism deals with belief.
So what do you know, and what do you believe?