I gotta agree some of these are really vague. I've seen plenty of rape-as-plot-device in comics, so unfortunately there should be tons of material for you there. :/
I've seen waaaay more man-on-man rape come of manga works than I care to remember. It's worse when the fans see no issue in it at all. It's like stepping into bizarro land from the way western comics culture has portrayed women. D: