For me? It's gotta be Futanari Alchemist Triss is Horny for Sex: It's Not Rape if They Eventually Enjoy It
>fun gameplay
>lots of scenes with a variety of girls (all cute)
>loli
>Triss is basically Rance but cute so she's able to even more easily get away with being a serial rapist
>they eventually enjoy it
It also shows that male protag games work fine. I don't mind futa-on-female, but a game like it where you're a dude would be perfectly good and fun (and you don't even have to be a crusty old pervert because Triss is a cute young pervert). It kind of torpedoes the cope that male protag games don't work.