Well, I didn't view porn what's the correct verb?
until after I joined this fandom and I continue to think that I don't care about porn with actual humans (hentai can work though, also fucking lol at the Wikipedia page for hentai having actual hentai images including non-explicit lolis). So in addition to actually viewing porn, >yuri sex>futa, although mostly just magic futa on female>teats and anatomically correct horsepussy in general (although real horses mostly don't do it for me)>tentacles>horns and wings, somewhat
Winking and leg twitches are fucking hot, too.
I'm not sure it's a full-blown fetish, but ponies in socks are definitely cute and/or hot as fuck, similar with glasses and other simple lingerie; teacher Rarity is probably going to have me develop a proper liking for stuff like uniforms and such, too.
I've fapped to pic related even though it's >humanised, the socks are definitely a big reason for that but I do have a soft spot for these horned/winged humanisations.
Finally, I've noticed that a big part of why I like the porn I particularly enjoy are the facial expressions of the character(s), great expressions can make something a lot hotter. Does that count as a fetish too, ie. stuff like bedroom eyes and ahegao?