I run three Charizard sets as of late; one Zard X set and two Zard Y sets for singles and doubles.
BOOM. Mind Crush! (OHKO!)
EVs: 252 Atk / 252 Speed / 4 Def/SpD
Nature: Adamant
Moveset:
Flare Blitz
Dragon Claw
Brick Break
Dragon Dance
Set Details: This set is a counterpart to the typical Dragon Dancing set that is the exact same except Earthquake is replaced by Brick Break, making full usage of Tough Claws, and defeating Heatrans all the same. Like the EQ set, Charizard's biggest goal is to get up one Dragon Dance and start sweeping. A Jolly nature is not really necessary because Charizard won't be setting up in the face of Excadrills, or trying to speed tie anything at 100 Base Speed. The extra damage output is especially helpful in obliterating Mega Venasaurs and the like. Often times as Charizard begins to Dragon Dance in the face of Ferrothorn, Tyranitar switches in to try to counter and threaten Charizard. A +1 Earthquake won't kill, but a +1 Brick Break definitely will.
The only pokemon that "walls" Charizard's attacks with this set is Azumarill, but if you are unable to remove Azumarill from the game before you find the last chance to Dragon Dance and you have no other choice but to keep your boosts, you can easily 2HKO most Azumarills with Flare Blitz. The other few pokemon that can stop Charizard are Prankster Twavers which sacrifice themselves so that their teammate can come in next and revenge kill Charizard, and some of the most defensive pokemon in the game such as Mandibuzz which can hit back extremely hard with Foul Play, and Gliscor which threatens Earthquake.
C-C-C-C-COVERAGE FTW
EVs: 252 SpA / 252 Spe / 4 SpD/Def
Nature: Modest/Timid
Moveset:
Flamethrower
Solarbeam
Focus Blast
Dragon Pulse
Set Details: Charizard has an amazing spectrum of moves, almost everything it needs to handle everything in the meta. Fire Blast isn't necessary over Flamethrower because Flamethrower does all the damage you'll need, and the misses aren't worth it. In many situations, you'll find that your opponent is definitely going to switch out with his Ferrothorn, but a good Sun-Boosted Flamethrower will do more than Stealth Rocks or Spikes damage to the pokemon coming in, even if it's resisted. Like any other special attacker in existence, Charizard can't touch Blissey, but like any smart trainer who wants to effectively use a special attacker, you should always have a safe counter to deal with Blisseys that won't get Toxic Stalled to death. Solarbeam is incredible on Charizard, as water types no longer function as counters to Charizard. Even if they are fairly bulky, a combination of Flamethrower on the switch in and Solarbeam next will toast almost all water types. Most of the pokemon that give Charizard trouble are fast Electric/Rock type users like Jolteon, Manectric, Garchomp and Aerodactyl, so Charizard fairs wonderfully with Sticky Web support, allowing it to easily OHKO Jolteon and Manectric with Flamethrower, and pick off a non-full HP Garchomp with Dragon Pulse. Charizard also appreciates a little bit of team support for Aerodactyl and Thundurus.
Versus teams with Tyranitar, you can often predict the switch into Tyranitar and attempt to fire off a Focus Blast without having to worry about the consequences of missing your attack. From then on, you can feel free to preserve Zard Y for any Ferrothorns that the rest of your team can't handle, or try again with Focus Blast with no regrets, if the first one missed or didn't kill because Ttar is Assault Vested or something. Sometimes you'll have a reason to stay in and risk the biscuit if Tyranitar runs Pursuit and you know he's going for it, but otherwise with this set, Charizard's threats and counters fall to just Blissey, Chansey, other special walls like Goodra and Florges, Thundurus and Zapdos who can't be slowed down with Sticky Web, and fast Scarfers with Rock attacks.
EVERYONE DIES TO THE ALMIGHTY FIRE
EVs: 252 SpA / 252 Speed / 4 SpD/Def
Nature: Modest/Timid
Moveset:
Heatwave
Solarbeam
Dragon Pulse
Protect
Set Details: Unless your opponent has brought specific counters just for Charizard alone, they'll find themselves getting double OHKOs from Charizard's devastating Sub-Boosted Heatwave. Only pokemon with high special defense or a resistance to Fire can survive just one Heatwave. This set features the sheer power of Charizard's almighty destructive fiery power in doubles. This set is primarily meant for the VGC setting, however it works well in any Doubles setting for the same reasons. With Charizard simply on the field, way over more than half of the pokemon in this meta are threatened. Charizard can deal quickly with Azumarils and other water types before they can set up. A Modest Charizard Y will OHKO a Politoed with no special defense investment with Solarbeam. With common and powerful Doubles support strategies like Tailwind and Thunderwave, Charizard can out speed all its threats, OHKO Salamences, Greninjas and Manectrics. With a little Quick Guard or team support, it doesn't have to worry about those Choice Banded Talonflames.
Charizard in Doubles does have to worry about Mega Kangaskhan's powerful Return attack, Garchomp's, Ttar's and Aerodactyl's Rock Slides, and Choice Banded Talonflame, however with the right team support, it can easily be one of the most threatening pokemon in the entire meta.