I know the poll is ancient, but it's missing the thing I'm actually looking for: a guy who cheats on his girlfriend. I don't want a harem if that implies you're not cheating. I don't want a polycule; I want infidelity. I want the girlfriend to be absolutely devastated if she ever finds out.
I don't want the girlfriend to cheat. I want her to be sweet and wholesome, and totally undeserving of the misery her boyfriend will eventually put her through. Nothing turns me on more than guys cheating on their innocent girlfriends/wives with much sexier girls. I want them to gaslight her as they get increasingly more blatant about their affair. Or I want her to secretly discover the affair and meekly pretend she doesn't know her boyfriend is fucking her best friend