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I could easily see an Aegislash holding Leftovers since Shield forme is so bulky and it would rely on that forme to take hits and keep it from fainting.
Also, Mega Medicham would not appreciate a Shadow Sneak to the face at all.
Well Eevee is catch-able rather early in the games, and I don't think that Game Freak would exclude Glaceon and Leafeon's evolution methods from X and Y.
That has been known for quite a while. Search the thread for information next time.
Repeating already-confirmed information just slows the thread down. :)
Well, it makes sense. You can only Mega Evolve once per battle, so once your Key Stone has been used and your Mega-Evolved Pokemon faints, you're out of luck until the next battle.