This has already been taken too*counter*
Gyarados @ Lum Berry
EVs: 252 Atk / 4 SpD / 252 Spe
- Tera Blast
- Dragon Dance
With Gyarados, not only can you easily switch it in on the quiver, you can then choose to either ohkoe or setup a ddance if you wish to.
Additionally due to all of volcs moves being resist, switching in on it even when it is already plus onez you will still live and be able to ohkoe it back.
Additionally Gyarados loves to run lum berry as it hates burns, so this means that if even if you get flame bodied, it will remove the burn and you will be +1 from moxie.
+1 252 SpA Tera Ground Volcarona Flamethrower vs. 0 HP / 4 SpD Gyarados: 113-133 (34.1 - 40.1%) -- guaranteed 3HKO