Aww, Niek :-)
Mine was Lawrence of Arabia. I was a child and I walked into a "classic" cinema room by accident with my sisters. We wanted to see a childrens movie. I did not understand anything but I could not sleep for weeks due to all the cruel pictures. For some reason we were afraid to leave the theater thinking we would not be re-admitted for the right movie.
I don't even remember... but maybe mine was Spider Man 1. I'm not sure. Maybe I had been to the cinema before Spider Man came out. I can't remember now. Pity.