I thought about going to a church (with a video camera hidden somewhere) and faking an experience, like when they offer up the communion, eat the waffer, then start screaming "it burns, it burns" and fall to the floor and go into a fake seizure. Then go into a whole routine making it seem like Satan is being expelled from my body (maybe have a friend flip the lights on and off for effect). Then stand up acting as if you're possessed by Jesus.
Unfortunately this would strengthen the beliefs of those in the congregation, but it would make a damn funny YouTube video.
Another thought is to go into the church on a Saturday and set up a bunch of special effects. Replace all the candles with self-igniting candles (they're built like a butane lighter with an electronic solenoid, supply the candle a voltage through the wires sticking out of it's bottom and the candle lights, remove that voltage and it goes out). Then patch into the PA system, and maybe even set up some really powerful floodlights outside the stained glass windows. During the service, make all the candles go out, then relight, maybe play a really low frequency over the PA, one of those sounds so low you don't really hear it, but you feel it, like a freight train in the distance. Do all this to get their attention so they all believe they're experiencing a true religious experience. Then with a vocal effects processor on the PA system, figure out what you want the people to hear "directly from god" and say it into the microphone. I'd probably make some kind of speech saying things like "you judge others in my name, but you're no better than them" or "you understand that I created all humans equally in my image, so why do you condemn those who don't believe in me".
I think someone could have a lot of fun with something like this, and if it's believable, this might just change some opinions in the congregation. Talk a lot about compassion for your fellow man, then run outside and dress like a homeless man holding a cup and watch them pull out their check books.
