Well, I was raised into Christianity (non-denominational for those who are curious), and I am going through a crisis of faith at the moment, but I was never discouraged from critical thought so I've had doubts about the existence of God until some time last year.

I was at the eye doctor, and sitting in the waiting room trying not to have a panic attack and burst into tears. (They were doing tests for glaucoma and going blind is something that deeply terrifies me.) All of a sudden, this sense of peace that I have NEVER felt before or sense just...came over me, and it was a deep, otherworldy peace. In that moment, every fear, doubt, concern etc. was gone. And then the feeling went away.

I did finally burst into tears when I went back in to talk to the eye doctor when I told her how afraid I was. She told me that I don't have to worry about glaucoma, as far as she could see, my ocular nerves looked way too healthy for it.

So yeah, that event cemented my belief that there is a God. As far as I know, it can't be explained away as supernatural.