According to the Sun and Moon story, Alolan form Ninetales can produce ice crystals from its fur. It can use them to block attacks or turn them into powerful ice missiles which can shatter rock.
Fairy-types have proven themselves to be fairly powerful in the X & Y games, so it's pretty cool that Ninetales gets an upgrade in that way. I'm not so sure how I feel about Vulpix and Ninetales becoming Ice-types, but they could end up being pretty decent. Now that they are no longer weak to water, but now weak to Fire, Rock, and Steel, it changes entirely how they will be utilized.
Of course, these changes only apply to the Vulpix and Ninetales actually caught in Sun and Moon. I'm looking forward to seeing just how well the Alolan forms of these two fit into my team in the future.