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Abomasnow and Mamoswine are quite good. So is Kyube, if you want to count legends.
Cloyster is a poke that, imo, is shit in OU, but we can't deny it's sweeping potential. It'd be broken in any other tier anyways.
Weavile is decent in singles but awesome in doubles. Same for Jynx, though Jynx can be a beast in singles if you know how to play to it's strenghts.
Regice is kinda cool as well, but we all know defensive ice types are never a good idea.