So I have been experimenting with Mega Mewtwo Y. Very unpredicable pokemon, probably the most unpredictable Mega Evolution to date. Mainly, I have been playing around with Low Kick Mega Mewtwo Y. Unlike Aura Sphere, Tyranitar without a Chople Berry is shredded by a Low Kick, and Sp. Def Dialga and Normal Arceus do not like eating one either (Mega Mewtwo Y can take a Draco or two from an uninvested Calm Dialga, 120 base Sp. Def ftw!). It also doesn't miss like Focus Blast BTW (even though when using taunt, you can buffer yourself from threats like Ekiller preventing them from setting up). I've been playing around with this set.
Mewtwo & Mewtwonite Y
Hasty Nature
EVs: 4 Atk/252 Sp. Atk/252 Spe
Moves: Low Kick
Psystrike
Fire Blast/Taunt
Shadow Ball/Ice Beam/Taunt
I found that this Mewtwo is best used on Sun teams so that Fire Blast does a lot of damage to Darkrai, even though Darkrai wouldn't like switching into a Low Kick (2HKO). Like I said, unlike many other Mega Mewtwo Ys, this set does not make Mewtwo Pursuit Ttar bait. Without taunt though, it might be best to pair it up with a wallbreaker such as Darkrai, as this Mewtwo is even more sensitive to status, being that it also uses its attack and doesn't like the burn. What does anyone else think?