Showgirls you may recall was the first NC-17 to get a wide rating. Here's every NC-17 film:
I know that there was a now-forgotten controversy concerning the film Angel Heart, from 1987, where Mickey Rourke and Lisa Bonet have sex in a leaky home and the raindrops outside turn into blood with blood being thrown all over them while they're doing it. But that was three years before NC-17 which was established in 1990.
I wonder why Freeway, my favorite 90s trash movie, almost got it. I mean it's about a teenage prostitute but so what.
The Godfather Part III almost got it? That'd be hilarious! (I've completely forgotten most of what happened in that film.)