Fetish
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Just erotic, nothing kinky. It's the difference between using a feather and using a chicken.
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A sexual Fetish (or, more properly, a paraphilia) is getting turned on by something that isn't considered a normal turn-on by one's culture. Of course this means what is considered a fetish will vary, and puritanical cultures will even consider any form of arousal to be taboo. Anything that isn't a normal turn-on could be a fetish. That is the other reason not to go into a detailed description of what exactly a fetish is. In fiction, there are general clues to show what's being treated as a fetish—namely, how people react to someone being aroused by something. If people are either disgusted or uncomfortable talking about it, it's generally a fetish. If people are impressed, it's kinky, but still on the edge of normal. Handcuffs can easily slide between fetish and kinky this way.
It's still uncommon to see a fetish openly discussed in mainstream fiction, and rare to see those with a fetish not treated like weirdos. This is slowly starting to change, however - in the 2010s the psychiatric profession significantly narrowed the number of what's considered to be "pathological" paraphilias to only cases where significant harm is inflicted on oneself or another person (which means that, yes, doing it Safe, Sane, and Consensual isn't considered to be "significant harm"). This reduced list leaves out particular body part fetishism (like, for example breast or ass fetishism) and certain object fetishisms off the list of what should be treated "on sight", moving them into a "treat on case by case basis" category. This means that treatment is only reserved for cases when a fetish (not including the "harmful" fetishes, which are considered a separate category as explained above) becomes such an overbearing part of sexual experience that it actively causes distress.
For a partial list of recognized fetishes, see That Other Wiki.
A Super-Trope to Casual Kink, Hemo-Erotic.
Compare Rule 34, Rule of Sexy, Fetish Fuel (when something in media sets off a viewer's fetish, while this trope is when someone on the show is turned on).
No real life examples, please; as mentioned on the Fetish Fuel page, everything is a fetish for somebody.