Hmm.. let's see..
Futanari - I don't know; I blame Fakku for this one. Something about watching a girl be able to take her orgasms to a whole new level, both by feeling it herself and by showing it through bodily fluids, is just amazing. Uno Makoto in particular makes my favorite futas.
Ashikoki - I've always loved feet. Not sure why. Hentai feet usually bore me, but when drawn right, I love it. See Cl-Orz 17, I think?
Glass no Karen includes both futa and ashikoki, and exemplifies hentai feet that I like.
Ahegao - Again, it has to do with my love for seeing women have unimaginable orgasms. Alice no Takarabako.
Cheating/Housewife/Incest - I'm starting to like these. Not as harsh as Netorare, but there's still a small thrill of doing something looked down upon. Also, there's always room for more MILFs.
Anal - Now this is fairly new. Usually when I watch pornography of real people, ass-play is just boring.
Nikuyoku Analyze Chapter 4 is what made me like anal. Some people might not like the gaping butthole, but I sure as heck do. Also includes housewife and cheating.