(Finished the first Mass Effect! Now I'm trying to get back into good writing habits and complete some projects before ordering ME2.)
Trope: Violently Protective Girlfriend
Description: Do not mess with the boyfriend of the Violently Protective Girlfriend. It will not end well for you. Just as mothers instinctively protect their children, the Violently Protective Girlfriend does not want any harm to come to her chosen partner under her watch (and if something does happen, she'll feel really really bad about it). She's usually adept when it comes to self-defense or physical fighting, whether she has powerful weapons of doom at her disposal or nothing but her bare fists.
Examples: Sarah from [one of my favorite shows] Chuck, Katniss from The Hunger Games, Zoe from Firefly
Pros: It should be no secret by now that I loves me some badass women. I think women can (and should!) be heroes just as easily and often as men. Having the knight in shining armor protect his damsel in distress is a much more common plot; there's nothing wrong with turning things upside down every now and then. (Note that this trope differs from the Badass Damsel.)
Cons: If a man constantly needs his woman to protect him, it can be seen as emasculating. In romance, that might make the male lead less conventionally sexy. There's a reason the aforementioned "man saves woman" plot has been so popular for so long. Overly tough, aggressive women can also be difficult to relate to in the context of traditional romances.
Would/Did I Use It?: As I said up there, it's obvious by now I like strong female characters. Ro from Disintegration could fall into this category, and a case could even be made for Liora from The Edge of the Sphere. I'm not going to give away any spoilers for the in-progress Searching the Skies sequel, but...let's just say this trope might come up eventually....