Proof that there were 13 women at the Last Supper!
My favorite is the assertion that Constantine decided the canon, that is, that he decided which books of the Bible would be authoritive. This is not supported by documentation, in fact, he relied on other theologians for his spiritual leadership. He called for meetings to decide how the church could be organized, but only made recommendations; he did not try to shape theology. As this book will tell you, he did not care about having too many specific points in his belief system; instead, he was interested in helping the different factions of the church agree on some basic principles so they could be united.
The canon is usually attributed to Athansius, who lived at the same time as Constantine but was certainly not his friend. (After Athanasius' recommendation, the canon was further scrutinized and discussed by the church so it cannot be said that any single person made the decision.)
Listverse.com has a fantastic article on this and the real reason I set up this blog entry was so I could simply point you there - but I got distracted and wanted to write about Constantine. Enjoy, and tell your friends not to be afraid of albinos. Here's the list.