Winner: Ar tonelico
NIS America | PS2
Anime-infused RPGs are a niche within a niche, so there's a rather large chance you've never even heard of this, let alone played it. The RPG bits are all intact and perform fine enough (especially the nail-biting battle system), but what really made Ar tonelico stand out was its bizarre pseudo sex storyline involving the main character and two perfect-bodied anime babes.
Like all RPG ladies, Misha and Aurica can use magic. But in order to unlock new levels of power, you have to "dive" into their minds and explore their innermost emotions. Loads of sexual innuendo ensues, culminating with the introduction of alarmingly phallic Grathnode Crystals. Aurica and Misha have "ports" on their bodies you have to "insert" the "crystal" into so they can gain new abilities. Misha is totally comfortable with her body, basically begging you to poke where you please, but Aurica keeps lodging concern - "To be honest, I'm a little scared, since I've heard that it hurts when you put it in." Just watch:
"As long as it's you, I can take the pain."
Honorable mention: Conan
THQ | 360, PS3
We realize that grunting, half-naked slabs of rippling muscle aren't what most gamers think of as "sexy," but Conan overcompensates by making its hidden power-ups topless chicks in bondage who writhe seductively when you free them. Beats the hell out of making Master Chief track down skulls, at least.