IAs for rape I stay away from it because I have found most of my players male and females don't want it in game.
Though I have had female players have rape in their backgrounds as character motivation on why they adventure.
I use it as a story telling tool. It's an emotional subject that gets players fires burning. But, it can be over-used. I try not to do that.
I really can't remember the last time I used rape in a game, but in my current game, my players were afraid that the little 4 year old girl would be raped by the enemy clan that took her. It was kinda like being on the western frontier, and the savage indians took the settlers' daughter. Think the Ron Howard film The Missing.
But, that didn't happen in my current game. As I said above, they cut her tongue out, but they didn't violate her sexually.
Not all bad guys are interested in that kind of power. These guys in my game are enthralled by a demon, so they're more the type to sacrifice the little girl in a ritualistic fashion rather than rape her.
The demon, though, is worshipped as a god by some peoples, and one of his aspects is rape. A god of strife and mysery, rape, battle, and destruction.
This type of dark grittiness has a home in the Conan universe. Heck, I remember reading a Marvel comic where Conan is magically forced to have sex with dead women--zombies. And, that was from the 70's. I couldnt' believe that the scene got past the comics code back then.
And in reading a favorite series, Thieves World. One of the characters was cursed by a god to live forever. And, in that god's background, the god raped his own sister. There is a Thieves World story where the god is trying to get his deciple to do the same to his sister.
Greek mythology is filled with this type of stuff. It's even shows up in the recent Clash of the Titans remake.
Presentation is not as gritty, though, I'll grant you.