I'm going to open Pandora's Box here and suggest:
Rock / Ice (or Ice / Rock... apparently there's no difference?)
Looking at that, most people would think it's the worst possible typing. And it probably is. I doubt I even have to explain why. Like any other type combination, it does have a few pluses that are worth mentioning. More than that, though, this kind of typing will probably cause the most interesting discussion, the most controversy, and the most use out of every future stage of this process.
Let's look at its positives and the likely role that Rock / Ice will take. Looking at its numerous weaknesses, mostly to very common attacking types in OU, it is probably doomed to be a hit-and-run attacker (not necessarily Choiced). It does have some advantages in this regard. Physical Rock-type STAB and special Ice-type STAB can be rather useful, and the typing can benefit from both sand and hail.
The weaknesses, also, can be put to use. I normally wouldn't even list them but even I need to keep track of them: Fighting, Grass, Ground, Rock, Steel, and Water. Keep in mind that Grass- and Ground-types are threatened by Ice STAB. The other weaknesses mean that Rock / Ice CAP would mainly lure in Tyranitar, Terrakion, Water-types, and the priority users Scizor and Conkeldurr. Depending on what we do with the future stages, we could use this to Rock / Ice CAP's advantage to give the aforementioned a hard time somehow. It's hard to elaborate without poll-jumping, but it's certainly possible, and perhaps a new niche will be created out of it.
The thing that really gets me about this typing is that it is so incredibly bad, and yet the tools available to us are still powerful enough that we can accentuate the few advantages that it does have. The process resulting from this would probably run counter to most of the CAP processes from the past; instead of being tasked with a balancing act throughout the process, this project would be "balanced" right from the start. What we usually see as flaws in the process can be turned around and used to our advantage. In fact, we'd most likely have to do so, at every stage, ironically reducing the risk of one aspect "replacing" the typing. To anyone who has ever wanted to see the very being of the CAP process turned upside down, just to see what would happen: THIS is your chance.
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