I know what you mean by this. I consider myself an atheist, but in my moments of complete despair and desperation, I try and talk to God. In 20 years of my life, God hasn't answered, sent me a sign, or even a little hope. Just pain. So, why would it be different in my last moments? He hasn't listened or answered in 20 years. Why would he at the moment of my death? Thousands of people die everyday in unfair, painful situations. They are forgotten. I'm just another one.
If God existed, I wouldn't need to do it in the first place. I wouldn't be this hopeless. There's also the point I would hate to find out there's another life beyond this one, and that all this was a test. It would enrage me, because it's not fair. I want to die and for all of it to be gone.
I don't want God to exist. Because if God existed, it would make me angry. If God existed, there wouldn't be so much suffering. If God existed, he would listen.
If God existed, I would still have a reason to live...