The Exorcist did it for me - whenever the camera started moving towards the girl's bedroom, you knew there was something nasty in there - including the green projectile vomiting and her head turning through 360°. My mate and I had hands over our faces, whilst our wives were laughing and smiling.
When we came out of the cinema (fleapit more like!) the Samaritans were standing outside, offering their help to people who had been disturbed by the film
