Charizard

VGC14, and by extension Generation VI, was none too kind to Dragon-types, nerfing Draco Meteor, introducing Fairy-types, and banning the premier Dragon, Latios. As if to fill the void, Charizard was given a new Mega Evolution that plays similarly to the Dragons of days old, with insanely powerful Overheats nuking any Pokemon that are not specially defensive (and even some that are), good coverage with Solar Beam, and reliable spread damage in the form of Heat Wave. As a twist of fate, its new ability Drought allows Mega Charizard Y to consistently defeat its long-time rival Blastoise, as well as more prominent Water-types such as Rotom-W and Politoed. Mega Charizard X was actually granted the Dragon-type and plays so differently from the more common Mega Charizard Y that it can turn a match on its head in the likely event that it can capitalize on that initial surprise. Dragon Dance allows Mega Charizard X to play similarly to Volcarona in VGC12, and although it does lack the spread damage option that made Volcarona so feared, it does enough damage to a single target to make up for this.

As always however, there are some catches to using Charizard. While it's difficult to KO it with Thunderbolts, Rock Slide from any decently strong Pokemon can quickly clip Mega Charizard Y's wings, and given the wide distribution of the move, it can come out of nowhere and instantly KO Charizard. It's also incredibly dependent on the weather staying in its favor, which means after it Mega Evolves, Tyranitar and Politoed can easily come in, wall, and OHKO Charizard with their STAB moves. In the same vein, Mega Charizard X is easily checked by Intimidate and faster Dragons such as Garchomp and Choice Scarf Salamence. This, and the fact that it doesn't have any spread coverage outside of the significantly weaker Heat Wave, makes it easier to play around, even if the opponent is thrown off by its surprise Mega Evolution.