If Shuckle has a Mega Evolution they should give the 100 bst increase to it's speed, and give it Stance Change where it becomes a fieresome looking worm.Shuckle, Meinshao, and Raichu would be really awesome. The thought of Shuckle having a crazy intense Mega form is hilarious to me. Meinshao is because I've been using one for my X playthrough and I keep thinking about how awesome it'd be with a mega. As for Raichu, that's mostly because its in the Pikachu line and I was a little surprised to see them not getting anything. You could increase its Special Attack and Speed a ton or something.
And MegaMeganium for Meganium's Mega xDI'm pretty surprised there isn't Mega Dragonite already. Although what would they call the stone? Dragoniteite? xD