Good old testimonials.
Christian "I had a vision in which Jesus appeared to me and told me things the future holds, but I can't remember what they are, so I can't tell you. That's why I'm a Christian"
Muslim "Really? I had a vision in which Mohammed appeared to me and told me things the future holds, but I can't remember what they are, so I can't tell you. That's why I'm a Muslim."
Christian "What? You expect me to believe in your religion on the basis of such a flimsy claim?"
Christian "I had a vision in which Jesus appeared to me and told me things the future holds, but I can't remember what they are, so I can't tell you. That's why I'm a Christian"
Muslim "Really? I had a vision in which Mohammed appeared to me and told me things the future holds, but I can't remember what they are, so I can't tell you. That's why I'm a Muslim."
Christian "What? You expect me to believe in your religion on the basis of such a flimsy claim?"
Playing Cluedo with my mum while I was at Uni:
"You did WHAT? With WHO? WHERE???"