Jedamethis said:
I'd tell the first man that there is no God
oh wait, no repercussions.....
Talk to Jesus?
He might have existed.
If you haven't already, read The Da Vinci Code
Admittedly it would be fun to say that to the first person to see what would happen to the world.
Jesus existed, that's pretty much fact. It's whether or not he was more than just a normal man that is up to debate.
The Da Vinci code was terrible and extremely loosely based on any truth. Angels and Demons was better but is also meant to be taken with a bucket of salt.