One time somebody walked up to me to tell me that Jesus was coming back soon, and we'd all be judged that day because I had facial hair and was wearing a dress, he was talking about the rapture. So I responded by looking at him and his family and saying "Only 35,000 people make it through the rapture. Unless you believe that you and your children are in the 35,000 most righteous people in the world, you're going to the exact same place I'm going in the rapture." He looked back bewildered and one of his kids started getting really upset

Walked by some Jehova's Witnesses in full garb and he tried to start some shit with me. I told him that as the holder of his wife's priesthood (she was standing by him), he was sending her to hell for letting her do a man's work of evangelism. That she'll burn in hell for the holder of her priesthood accepting false prophets (Watchtower society).

Met an asshole Mormon at a coffee shop and told him that he was going to end up in a telestial kingdom and his family would forget about him in eternity for consuming hot drinks. When he asked why I, an upstanding Mormon was at the coffee shop, I told him that I ordered cold ephedra tea just like Joseph Smith intended.

Another good one is if they're married but not with child, call the man a whore for not nutting in his wife. Wasting cum is a sin.

A lot of it is just that I have a serious knowledge base of the religions because I wanted to be a theologian when I was a kid. The best advice I have is that you probably know about as much as whatever christian heckler is fucking with you knows. Have a few common sins and failings on standby, and just be prepared to act like a zealot. They love inflicting it, but have no idea how to respond when someone else does the same to them.