Either Dohna Dohna or Koikatsu, though funnily enough I barely use the H-aspect of either game and just go through combat or character creator respectively
Not entirely sure about favourite, but first game that came to mind when reading the question was Degrees of Lewdity. Played that game multiple times throughout the years, especially when Flash was still around. Although you can't exactly consider it an H-game....
Been digging the largely text-based Degrees of Lewdity. The reasonable challenge + fast updates + shameless degen content really works for me. Another fav is the popular Karryn's Prison. I think I might just enjoy corrupting female protagonists, lol.