So, I've never watched hentai therefore I can't answer this question. I am very innocent and most people know that about me. I can't name any hentai. I've watched mainly romantic/comedies, harem/reverse harem, action/romance and some supernatural anime's. I don't know if B Gata H Kei counts but it's pretty close...So feel free to answer this question yourself if you've watched any and start up a conversion with someone in the comments.
I encourage all of you to do this challenge along with me, or just say in the comments what YOUR favorite hentai anime is!