I'm curious as to what sort of event or discovery would be enough to "prove" the existence of a god to you?
Would it be hearing the god's voice in your head? Would it be an event predicted in some holy book? The god rearranging the stars of a particular galaxy to spell "Yes I'm real" in every known language, as viewed from Earth?
A guest appearance would be nice. Screw the ephemeral stuff. Take a walk down every street and talk to everyone at the same time and do not leave, ever. Cure everyone of everything including the amputees this time. That should be a trivial trick for this god.
Carl Sagan, in his book Contact, proposes an interesting and clever scenario that would certainly raise eyebrows at least. I think the following would be a very good start for evidence of the existence of a sentient creator.
This is from Wiki.
"Ellie, acting upon a suggestion by the senders of the message, works on a program which computes the digits of pi to record lengths in different bases. Very far from the decimal point (1020) and in base 11, it finds that a special pattern does exist when the numbers stop varying randomly and start producing 1s and 0s in a very long string. The string's length is the product of 11 prime numbers. The 1s and 0s when organized as a square of specific dimensions form a rasterized circle. The extraterrestrials suggest that this is a signature incorporated into the Universe itself. Yet the extraterrestrials are just as ignorant to its meaning as Ellie, as it could be still some sort of a statistical anomaly. They also make reference to older artifacts built from space time itself (namely the wormhole transit system) abandoned by a prior civilization. A line in the book suggests that the image is a foretaste of deeper marvels hidden even further within pi. This new pursuit becomes analogous to SETI; it is another search for meaningful signals in apparent noise."
This could easily be done by an extraterrestrial technology that has evolved eons ahead of our own. Who was it that said that a miracle by the bible's standards would be indistinguishable from an extraterrestrial technology?
Ok, there have been some pretty creative responses, but I'm going to change the question a little bit now. What would be the LEAST amount of proof that would be required for you to start entertaining the idea that there is a supernatural intelligence at work in the universe?