What would make me believe in God?

When talking to religious folks we are often discussing the topic of evidence which commonly leads to the question: What evidence would cause you to believe in God?

To quote Aron Ra, a popular atheist on YouTube:

JESUS, I WANT A DOLPHIN IN MY POCKET.

Essentially, I would need a miracle, just like Doubting Thomas (a guy who really got a raw deal since his skepticism is considered a negative trait). If I were to call out to Jesus and request a dolphin in my pocket and BAM! DOLPHIN! ... I would become a believer. I would need some other people there with me so they could experience it and help verify that I wasn't just having a psychotic break. I'd also prefer to have a video camera running, obviously.

Not every other atheist would agree with me on this, however, and it would be totally justifiable for them to disagree because there is a difference between confirming the occurance of a thing and identifying the cause of a thing. Right? It is theoretically possible that some scientist on the other side of the planet turned on his experimental teleportation machine and it accidentally teleported a dolphin into my pocket. Or perhaps it could be aliens, etc, etc.

I could refine the parameters of my dolphin miracle to help reduce the possibility of those other options... the dolphin could speak and tell me the thing I'm secretly thinking and tell me which God sent him (just it case it was Allah), which would then rule out a normal dolphin and the scientist, but perhaps those aliens actually are telepathic dolphins and that would be incredibily easy for them. It's not going to be possible to truly determine a supernatural cause for a natural phenomenon. 

However, if I experienced something that far outside of natural occurences, I think it would be enough to convince me without the need for absolute 100% proof.