Diancie

Mega Diancie is a good anti-metagame Pokemon in the 1v1 metagame with its unique Rock / Fairy typing that, in combination with its good Speed tier, allows it to reliably beat metagame staples such as Mega Charizard X, Mega Charizard Y, and Mega Gyarados and serve as a good check to the ubiquitous Dragonite, only fearing Choice item variants. Furthermore, its pre-Mega ability Clear Body nullifies the effects of Intimidate from Pokemon like Mega Gyarados, while its post-Mega ability Magic Bounce protects it from status moves directed at it, ensuring wins against certain stall Pokemon like Whimsicott and fast sleep users like Jumpluff, Vivillon, and Smeargle. Diancie's excellent bulk prior to Mega Evolution allows it to delay Mega Evolution to beat Pokemon such as Mega Charizard Y, Porygon-Z, and Mega Gyarados. Mega Diancie's EVs are stretched thin, however, so it is unable to consistently beat Mega Gyarados and simultaneously outspeed fast offensive Pokemon such as Garchomp, Kartana, and Durant. Furthermore, the prominence of Steel-types in the metagame hurts Mega Diancie, as its 4x weakness to Steel is easily exploited by threats such as Heatran, Mega Aggron, and Celesteela.