I can think of many more we watched on cable that were inappropriate - but in terms of an actual trip to a theater, here's what comes to mind. Thanks for requesting, @gwcoffey, great topic!
  1. Saturday Night Fever
    My first R-rated movie. I think I was four or five years old. It was playing at the drive-in in Upstate New York. My parents thought I was asleep in the back of the car, but I watched the whole thing in fascinated silence. About 90 minutes in, I broke down and asked, "What does 'knocked up' mean?" At that point, they figured it was too late to tell me to go to sleep. Still love this movie, an honest-to-God masterpiece with such a moving ending.
  2. Rocky Horror Picture Show
    It was inappropriate for my father to take me to see a movie about gender confusion, "homosexual panic" and shame-based, violent sex displays when I was in 7th grade. It was even MORE inappropriate that he brought my sister, who was three years younger. I've seen the movie about 100 times since then. I love it.
  3. So I guess what I'm saying is, my inappropriate parents introduced me to awesome movies. Thanks, Mom and Dad! Off to therapy!