Ah... Charizard... This guy has one thing going for him (besides generally being badass) and that's the raw freaking power of his Sun boosted Solar Power Fire Blast. This thing hits like a nuke, but, that said, after a single Nasty Plot Ninetales hits just as hard, so there's really no reason to use him in OU. Here's a NU/RU/maybe even UU set you can run, but it's generally better to use against something that's going to switch out so you don't take damage while setting up your weather.
"252 SpA Life Orb Solar Power Charizard Fire Blast vs. 252 HP / 144+ SpD Lickilicky in sun: 417-491 (98.34 - 115.8%) -- 87.5% chance to OHKO"
Charizard @ Life Orb
Solar Power - Timid
252 Speed, 252 Sp. Atk, 4 HP
-Hidden Power (Ground)
-Solarbeam / Roost / Flame Charge
So put this out against some Grass type like Sceptile and scare it off while you set up Sunny Day (and pray it's not running HP Rock), and then toast stuff with Fire Blast. Hidden Power (Ground) hurts anything with Flash Fire that can stomach a Fire Blast. Solarbeam is generally what I carry in the third slot for bulky Water Pokemon, but Roost heals off Life Orb and Solar Power recoil, except he generally can't find an opportunity to use it. Flame Charge fixes his slight Speed problem, but, once again, he can't ever really find an opportunity to use it. Sunny Day is self-evident. Also, a Life Orb is used over a Heat Rock because he generally doesn't survive 8 turns, but a Heat Rock can be used if he's on a dedicated Sunny Day team.