Dawn said she would use it in her contest. I can't see how any of her pokemon could do that. Piplup devouring his whirlpool? Mamoswine his ice-shard/ancient-power? That would be weird. I mean energy-ball is a ball of energy, and so mighjt be sucked into, but I dunno if it should work similarly for other attacks.
My only guess is Mamoswine ingesting Ancientpower or Hidden Power...kinda fits that it would.