I just hope that Torterra gets a mega evolution one day!
It begins with a little turtle and it evolves into this big turtle with a tree on his back.
How about a mega evolution with a small forest ?

In addition to what I said in my previous post, I would also like to see Mega Yanmega (for the name), and Mega Torterra. Mega torterra would likely look like an ankylosaurus, and have increased defenses and Attack. It would likely be Grass/Rock. Mega Yanmega would be a good Bug/Dragon.

 Mega Porygon-Z would be great. It'd have even more Special Attack, increased Speed, and be a Ghost/Normal type. I'd keep Adaptability.

Mega Slaking would be awesome. I imagine it looking like a larger, more menacing Vigoroth and losing Truant. More Attack, HP, and Speed. It'd probably be Normal/Fighting, with the ability Tough Claws.

Sharpedo is in desperate need of a Mega. It always seemed like an incomplete evolution line.

Metagross is losing its relevance in the competitive scene, and would greatly benefit from a useful Mega with higher stats all around.

I don't think a single Unova Pokemon got a Mega in X and Y, and that seriously needs to be fixed in Pokemon Z. Unova pokemon that deserve megas would be Klinklang, Archeops, Gothitelle, Reuniclus, Chandelure, and Eelektross.

 

Pichu/Pikachu/Rachiu

I would have to say hydreigon, metagross, salamence, all fossil pokemon, dragonite, flygon, and all starters