"Barbarella" was one of my favourites when I was young, there are a number of kinky bits in the "City of Evil" but I was blown away by the scene where Fonda is subjected to "pleasure torture" in the mad scientist's machine.

It taught me that in erotica, as in other art, suggestion can be more powerful than showing everything. You never see what the machine is doing to her, only her reactions, but that means you can imagine it's whatever you'd most like it to be.