Which of the current mega evolutions is your favorite or do you think is the best designed?

I’m very fond of Mega Sableye, personally.  Mega Evolution is a process that creates a crazy-overpowered super battle mode, not something that’s meant to exist as a realistic creature – it turns Pokémon into exaggerated versions of themselves.  I think Mega Sableye lugging around a massive jewel that it uses to reflect attacks (hence the Magic Bounce ability) is a fun, quirky way of doing that.