Rapidash @ Firium Z
Ability: Flash Fire
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Flare Blitz
- High Horsepower
- Wild Charge / Morning Sun
- Will-O-Wisp
Rapidash @ Life Orb
Ability: Flash Fire
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
IVs: 29 HP
- Flare Blitz
- High Horsepower
- Wild Charge
- Morning Sun

Rapidash @ Choice Scarf
Ability: Flash Fire
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Flare Blitz
- High Horsepower
- Wild Charge
- Megahorn / Sleep Talk

Additional move options: Sunny Day, Solar Beam
Additional item options: Leftovers, Electrium Z
Notes: 29 HP IVs on the Life Orb set reduces Life Orb damage taken, after the third attack Rapidash will have lost less HP than if it were running 31.
Rapidash can run Firium Z with Will-O-Wisp instead of Morning Sun.
There is a lot of loss in power for Rapidash's coverage moves by giving up Life Orb. 
Rapidash wears itself down very quickly without Morning Sun to keep it healthy. 
Leftovers can be used over Life Orb to increase longevity at the expense of damage output.
Sleep Talk on the Choice Scarf set is very good for webs teams, checking Spore Smeargle.
A Z-Sunny Day set can be used on sun teams to get a +1 boost to Speed and boost the power of Flare Blitz greatly. 
Z-Wild Charge can be used to 2hko physically defensive Poliwrath and greatly damage other such bulky water types, but is generally inferior to Firium Z.