Maniac was the movie that got me started collecting bondage scenes, the very first segment on my very first compilation tape (out of over 100). They say you always remember your first, and IMO, this is still one of the greatest mainstream GIMP scenes ever made, if you don't mind the fact that it's also a GIMP snuff scene.
I think it succeeds on so many levels. Number one, Abigail Clayton was beautiful. And early on in the scene, the suspense builds when Frank (the maniac in the title) knocks on her door and gains her trust by returning a locket she had lost, but what she doesn't know is that at the same time, he unlocks her door. Touched by what she thinks is a kind gesture, she thanks him, closes the door and proceeds to strip off her clothes and take a hot bath. At this point, we now know something bad is going to happen to her, and in a way, we're the ones stalking her, watching our beautiful prey strip down and relax in the tub, knowing she will be soon be our victim.
Then of course, you have the classic surprise takedown as Frank grabs her and knocks her to the ground, and when we see her next, she's securely tied to the bed and gagged with a scarf. This is where the scene really becomes suspenseful. Frank gets up on the bed and straddles her, takes her gag off and proceeds to ramble on about he loves her and now he's got her and he'll never let her go. And Abigail's reactions are tiny little horrified gasps, followed by a subtle tugging at the cords that are binding her wrists. She's totally helpless, and you can see it in her eyes and her reactions, but she's trying not to upset him. It's really two incredible performances going on, Frank as the scary, determined psycho, and her as the frightened victim who's trying to stay calm.
Then Frank pulls out a switchblade and snaps open the blade before her eyes (followed by another agonized sigh from his victim) and proceeds to run the sharpened point of the blade all along her bare skin. She pleads with him not to kill her, but he just roughly pulls the gag back into her mouth. He gets up real close to her and glowers down upon her, and now her gagged face fills the screen in close up. It's almost as if we are the killer and this is our point of view. You can really feel the sexual tension.
Then comes the knife into her chest (very realistically done) and that's sort of the orgasm of the scene, if you'll excuse the disgusting metaphor, but I really think that's the way the filmmaker intended it.
I used to feel guilty getting turned on by that scene because I was essentially getting off on seeing a woman get killed. But watching the scene again, it's just a masterpiece of GIMP-dom, very dramatic and worth seeing even if snuff scenes disturb you. It's part of what made me a perv today.