I choose Polkaroo, my female Scrappy Kangaskhan.
Do we know how all the Mega Evolutions will be handled? Some Mega Pokemon, like Mega Abomasnow, have the same ability and typing as their pre-Mega counterpart, so they just undergo a base stat change, except we don't really follow base stats at ASB. Would Mega Abomasnow's attacks just do more damage than regular Abomasnow's?