>>16565550Kanga is very strong, but also common because of that.
Ampharos is underappreciated, shockingly bulky and high Sp Atk, but doesn't really have a strong reason to chose it as your mega besides liking the design.
Scizor just doesn't bring much to the table as a mega. It just gets better stats. That's it. They aren't even spectacularly good.
Medicham is a beast, but like Ampharos really doesn't have a strong "oh shit look what you get if you pick him". He just because more powerful.
Gardevoir I don't think is worth using. I've yet to be impressed by one.
Banette, sadly like
>>16565636 said, just sucks. The only reason to use it is because you want to use Mega Banette. The movepool, stats, and ability just feel miss-matched, plus your Prankster doesn't kick in until the turn after you mega due to turn orders being set already. Just a disappointment.