One of the features in the upcoming Mass Effect is the ability to choose your gender. For a game which revolves around one central character (Commander Shepard) and the related storyline, it's an interesting addition, though not entirely novel.
However, it may have more appeal than a first glance would imply. We spoke to several female gamers at E3 who insisted that being able to play a female character is a crucial differentiator between games they like and games they love. It doesn't strike a game from the favourites list -- many of these women loved Halo 2 -- but it's a selling point that turns out to be surprisingly important to the female audience.