How dare you all insult Skyla! She is the best thing that ever happen to Pokemon, and my bias like for her will throw any logic out the window and praise her no matter what she did, or how she was written in the show. Skyla rules the region!
Okay, bringing my common sense back, and not wearing my bias Skyla cap on, She and Cilan's brothers are the only Gym Leader's in Unova I actually watched. I saw a little of Elesa only because Bianca was in it but the other Gym Leader's I did not watch their episodes so I can really only judge these ones. From what I saw, typical Gym Leader stuff. Nothing that really stands out or will make me remember them in the long run, minus Cilan because he's on the main cast. So really Cilan if he counts. Again I have only seen Cilan's crew, Skyla, and a single episode of Elesa, and if I take my bias for Skyla aside, they are all average to me.
Vote Glovehead for 2016's Pokemon anime female lead sidekick. #Gloveheadforfemalesidekick.