g-fig is actually an abrviation for the acronym gwpisutopifgs, which stands for girl who's personality is so undesireable their only purpose is for getting some.
It is generally used to desribe girls, but by simply replacing girl with guy it can be used in a very similar manner to desribe guys. Being a g-fig is much worse than being a chickenhead.
Dude, Ambria's such a g-fig, i'm definately gonna get a blumpkin from her. And get a picture of it.