omg Ninetales + Wishiwashi is so much fun
Ninetales sets up Hail + LC Aurora Veil, switch into Wishiwashi and now you have it's already insane bulk taking half damage. The constant damage from Hail is actually really beneficial as it allows Wishiwashi to control it's health better, having a much easier time getting into the range for Iapapa Berry to activate, which heals 50% health in S/M. By the time Iapapa Berry activates, Hail is pretty much always over so it's no longer a problem, while Aurora Veil is still up, allowing Wishiwashi to use it's restored health much longer than it usually would be able to. Plus, Wishiwashi has a slow U-Turn allowing it to safely switch back into Ninetales for Hail/Aurora Veil reset if needed.
also shiny wishiwashi is beautiful, it's eyes turn into goldfish
oh, and when switching almost everyone expects sandslash/beartic or ninetales to just stay in, leading them to use steel/fire moves, giving wishiwashi a super easy switch-in