I consider "douchebag" to be gendered only in the sense that it is anti-woman. But then, we know that even women can have anti-woman tendencies, so it works really well, all 'round, as an insult for people of both genders.

Shakesville used to have a funny in-joke where they would cry, "Release the douchehounds!!" It's funny only because of its sheer absurdity, though.