Curious44...this has the potential for a very interesting and informative thread. There are so many erotic scenes that come to mind that writing about them would take up more pages than 'War and Peace' and a congressional bill combined.
One of my favorites is a scene from the foreign movie 'Liz' in
which an attractive lady sits at an outdoor cafe and is admired by a stranger a few tables away. She notices him, but makes no move to acknowledge his subtle flirting. When she has finished her coffee, she pays the waiter and gets up to leave. She walks along the sidewalk occassionally glancing at the store windows to look at the wares. In one of the windows she can see the reflection of her admirer from the cafe. She pretends not to see him and continues her stroll. She decides to take in an afternoon movie and finds the theatre almost empty. She is seated somewhere in the middle row and is not aware that the stranger has also entered the theatre. He seats himself in the row behind her and at the end. From her focus on the screen she begins to look around her environment and spots the stranger. She quickly looks back toward the screen, this time appearing more apprehensive and fidgety. The stranger now moves closer and sits directly behind her. His arm starts to reach over and he rests his hand on her thigh. The woman does not move or protest. He continues his advance by sliding her dress up to the crease of her thighs and lower torso, revealing gartered stockings and silky full-cut panties. He then works his fingers into the 'mound of venus' and the woman is obviously getting aroused and aggitated in a sexual way. The groping and digital manipulation goes on for a few minutes with the camera jumping from her face to her crotch intermittently. Just as mysteriously as it started it ends. The stranger's arm leaves the woman and the stranger walks out of the theatre. The woman straightens out her dress and returns to her normal daily routines. The scene was so sexually charged that I could almost feel the warmth of her thighs and the wet, softness of her muff. The aroma de femina I could almost smell and taste. Needless to say, I've viewed that scene many times and will many more.
The idea of a stranger having his way with a beautiful woman in a public setting is high on my list of eroticism. The apprehensive willingness to submit to a total stranger also appears in the film, 'The French Woman'. A lady on a train is walking down the narrow walkway and decides to open the train window to breathe fresh air. She stands looking out at the passing country side when a complete stranger opens the door to his cabin and grabs the woman by the hips and draws her behind partly into his cabin. He lifts her dress and lowers her panties and begins to service her behind in a not so gentle manner. The woman in the meanwhile is holding on to the open window, never looking behind her to see who was seeding her derrier. When the stranger finishes, he simply closes the door, leaving the surprised lady to go about her business.
The two scenes I just mentioned were not acts of rape, but consentual and willing acts of random sex from strangers. It's as if the women someway anticipated or longed for such an anonymous encounter.
There are many other scenes that I find sexually stimulating such as in 'Summer of 42', 'The Lovers' with Victoria Avril and the one you mentioned, 'The Postman Always Rings Twice'. I used to collect such scenes from various movies and compiled them on video tapes and later to dvds. I must have over 400 such juicy little bits of heaven.