I got Mewtwo. He plays well but requires some technical tweaking of your Melee strategies.
He has no low sweeping attack (Ground DSmash), so his range isn't as good, but his DSmash is powerful to compensate for that.
His USmash won't has a smaller hitbox that's directly above Mewtwo so you can't use it to clear room in the ground. Only as an Anti-Air or as a juggle after a DThrow.
He can WallJump.
His Shadowball has ridiculous recoil/knockback when fully charged, so it can be used as a way to propel yourself away from an opponent in the air. Goes a bit far though with the slipperiness.