I recall at a young age, when I first became sexually aware, I had a notebook which I secretly used to document all the strange fantasies I had. Many years later, I rediscovered the notebook, and realized that even at that young age I had already developed most of my major fetishes - it really is all about childhood experiences, I guess. Below is my attempt to compile a list of my sexual interests, each with a short explanation concerning what particular aspect of it I find attractive.
Humiliation
This aspect, especially sexually-oriented humiliation, has always been a strong factor in my fantasies. Whereas physical rape isn't exactly a turn-on for me, psychological harassment, mind-rape for lack of a better term, is a much more elegant way of forcing an unwilling victim to participate in sexual activities - there is something very arousing about forcing a decent, well-raised woman to admit to her sensual/sexual side. Many of my other fetishes are in some way related to this basic kink.
Domination/Submission
The more basic 'control' fetish; verbal humiliation, physical intimidation, blackmail, restraints (bondage), punishment etc. can go a long way in breaking someone's spirit to the point where they submit, leaving them vulnerable and wide-open to further (sexual) humiliation. My attraction to this comes from (ultimately) mental control being stripped away from a woman, leaving her submissive (which works on a primal level for me) - it's subtle mind-rape. A powerful female dominant woman is also the villain of choice for me; male/male sexuality doesn't do anything for me, so femdommes are perfect when there are both males and females to dominate.
Hypnosis/Mind Control
A more invasive sort of mind-rape , the fantasy of using subtle commands, insidious triggers or whatnot to gradually warp a girl's mind towards a debased, lewd shadow of her former self is a great turn-on for me, especially when she's aware of what's happening to her but unable to stop herself, leaving her vulnerable to all sorts of embarrassing situations. The focus has to be on the gradual erosion of a victim's mind or will however; the journey is many times more arousing than the destination.
Forced Babification (infantilism)
Where hypnosis/mind control focuses on loss of mental control, specific parts of the infantilism fetish strike a chord with me for its loss of physical control, and the inherent social humiliation that comes with that. Control over basic bodily functions being taken away is inherently embarrassing ofcourse; being 'belittled' or 'babied' adds to that, which makes forcing baby attributes (diapers, childish dresses, pacifiers) onto an otherwise adult woman very arousing to me. Aside that, there is also something about a pretty but babified adult woman that's intensely cute, innocent and fragile, which triggers all sorts of protective instincts in me.
Latex/Rubber/Nylon/Spandex/etc.
The female form is simply a delight to behold, and anything that makes it look even sexier than when naked is awesome to me. This attraction can be as simple as a high-cut one-piece bathing suit to a full-body rubber catsuit, anything that gives a sensual texture or touch works for me; the more form-fitting, the better. Unfortunately this fetish doesn't always translate so well into stories because of its predominantly visual aspect, still, I won't be able to resist throwing sleek nylon pantyhose on powerful women in my stories.
Forced Transformation
This mostly involves unwilling half-way transformations into (mythical) animals, but other body modifications (breast enlargement, a woman growing a penis from her clitoris, replacement of bodyparts such as having a vagina as a mouth, etc.) work as well. The attraction for me behind this is that the women are forced into a more sexualized form; an animal has no social reservations about being naked or having sex, is considered a 'lower' creature, so I consider it inherently humiliating to be changed into a form like that - the process of transformation is an important factor in this. I also believe that a woman with some feral traits, be it physical or mental, can be a very exciting partner in bed. Finally, especially feline characteristics have always been regarded as 'sensual', and a catgirl thus works really well for me.
Costumes
A form of transformation-lite, costumes can easily carry a humiliating payload. The classic French maid uniform, an animal costume, baby clothing, a schoolgirl uniform: they all do a good job of embarrassing a girl not comfortable wearing them. I was recently introduced to the 'stuck' fetish which supercharges this attraction: girls wearing embarrassing costumes that they cannot get out of, forcing them to endure the full humiliation.
Dickgirls
As simple as a beautiful girl growing or having a penis (preferably combined with female genitalia); as a male I can very easily relate to the sensations and complications of having a dick. While male arousal and such isn't really a turn-on for me (as both reader and writer I'm already 'there' myself, another male isn't my thing), a woman with extra equipment, especially when she's not familiar with having it, can be really hot to me. Once again hooking into the humiliation theme, a dickgirl can't hide her embarrassing arousal as easily as a normal woman.
Sissification/Feminization
While normally I'm not really interested in the male viewpoint when erotic situations are involved, to me there is no form of humiliation more extreme than a male stripped of his masculinity, especially when physical female traits are somehow forced upon him as well - partial or full forced feminization, reduction of his male traits, forced crossdressing, etc. If the victim has been mentally/physically warped enough towards female, even male/male interaction can become interesting, but I still prefer reading/writing about males falling victim to a female dominant.
Amputation
Hooking in more with the domination/submission theme, I feel amputation, and especially quad amputation, is the ultimate manifestation of (realistic) physical control, as the victim has no chance to escape domination, and becomes dependent on someone to look after her, which in itself is an embarrassing thing again. I prefer 'clean' amputation (healed-over stumps) over blood and gore - while a part of me can really appreciate proper horror, it's not a turn-on for me; it's the helplessness and fragility of an amputee that attracts me.