M-Charizard Y is a pretty good fire-type with its high speed. But there are downsides to this fire Pokemon, because it is extremely susceptible to Stealth Rock, which already deals half of Charizard's HP upon switch in. Stealth Rock is pretty common among supporting Pokemon, like Smeargle, Shuckle and Ferrothorn for set-up, so I'd like to suggest something else:
I've did quite a lot of experiment in OU, and although this is kind of common, I still think Specs Volcanion is a pretty ideal attacker.
Volcanion @ Choice Specs
Ability: Water Absorb
EVs: 248 HP / 252 SpA / 8 SpD
Modest Nature
IVs: 0 Atk
- Steam Eruption
- Sludge Bomb
- Earth Power
- Fire Blast
I think Victini is also worth considering:
Victini @ Normalium Z
Ability: Victory Star
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Celebrate
- Searing Shot
- Stored Power
- Focus Blast
Victini @ Choice Band
Ability: Victory Star
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- V-create
- Bolt Strike
- U-turn
- Zen Headbutt
Lastly, Volcarona is fantastic, as well. This set goes exceedingly well. However, please beware that Volcarona takes Stealth Rock pretty badly too.
Volcarona @ Choice Scarf
Ability: Flame Body
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Fiery Dance
- Bug Buzz
- Hurricane
- Giga Drain
Of course there are others, but I strongly recommend these few.