This was difficult for me because I hate, hate, hate, hate, HATE the new mega evolution mechanic. I’m not going to rant and ramble about that, though, don’t worry.
On top of my initial dislike for the mechanic, a lot of mega designs look, well, stupid to me. They’re either too busy or too unreasonable or just plain silly. I do, however, like Mega Alakazam. It amuses me. So, I went with that one.