Things that go bump in the night. I personally like to do it during a thunder and lightening storm with curtains spread open and the windows up, the room is pitch black and every now and then you can see a shot of something something when the lightening strikes.
i dont think i could ever do light like completely on, i usualy dim the lights or pitch black so then you dont know whats going to happen.
I prefer candles and oil lamps or some other indirect lighting. I want to see but not have all the electric lights blazing away. In the dark is OK too but as a second choice.
last time i had sex with the lights off, my bf at the time slipped off the bed while we were changing positions and broke his ancle, lights on for me
on/off doesnt matter ons nice when i'm somewhere where there are lights but under the stars, far away from the nearest light is absolutely amazing