I don't want to include anything that has already been said, so I guess I'll include some personal annoyances:
Darwin did not turn to Christianity while on his death bed.
Christopher Columbus did not discover North America. He rediscovered it several hundred years after the Vikings. EDIT: Because a bunch of people are whiny pedants, let me amend this statement: I FUCKING KNOW THAT THE NATIVE AMERICANS GOT THERE FIRST. The first non-native people to find, oh, hey, another fucking continent outside of the ones we already know, was the Vikings. They, for all intents and purposes, 'discovered' North America.
The Constitutional Convention did not open with a prayer.
Thomas Jefferson, while owning slaves, was not pro-slavery, and drafted plenty of legislation that stopped the importation of slaves and the like, and made his state the first to stop importation of slaves from Africa.
Many/most of the founding fathers were deistic, and not strictly Christian.