What would be cool about that type combo is that Fighting/Ghost would not be able to scratch it (being that it is, in fact, the only typing that can't take shit from the combo).Ghost/Normal; I always wanted something typed like this, and the idea someone gave of it being Banette's evolution just makes it overall much more awesome.
Other than that, it was just Normal/Ghost that I wanted.
A pure flying type would also be nice, seeing we have none of those aside from Flying Plate Arceus. I've always wondered, ever since I first put my hands on a Pokemon game, why they were Normal/-, Water/-, Fire/-, Electric/Flying, etc etc yet there was no pure Flying type. I mean, Ghost was a dual type until GSC (lol Poison/Ghost -_-), but at least that was fixed by something other than Arceus!
Also, a cool typing would be Bug/Electric; the only weaknesses would be Rock and Fire (off the top of my head), and the thought of an electrically charged bug really amuses me for some really obscure reason.