Can anyone prove unequivally that God exists?

I've asked my Christian friends this thousands of times. All they say is that "you have to have 'faith' and just believe. If there were solid proof, it wouldn't be faith and you wouldn't be truly tested" or something like that....I am an agnostic because there is no proof either way (if I had to guess, I would say there is no god so I guess I'm kind of an atheist in that sense).