This is not a really a creative set, but an underrated one:
Arcanine @ Leftovers
Ability: Intimidate
EVs: 252 HP / 252 Def / 4 Spe
Impish Nature
- Flare Blitz
- Extreme Speed
- Will-O-Wisp
- Morning Sun
Fire types not really known for their defenses aside from Heatran, but when you factor in the fact that Arcanine gets Intimidate, it's defenses are greater than that of max HP/Def Impish Hippowdon. Calcs for reference:
252+ Atk Life Orb Lucario Close Combat vs. 252 HP / 252+ Def Hippowdon: 160-188 (38.09 - 44.76%) -- guaranteed 3HKO
-1 252+ Atk Life Orb Lucario Close Combat vs. 252 HP / 252+ Def Arcanine: 138-164 (35.93 - 42.7%) -- 94.34% chance to 3HKO
There are a few things that really make this Arcanine more effective in this gen than gen 5.
1. Because of the Weather Nerf, Morning Sun is a much more reliable form of recovery.
2. Fire types now have an extra resistance to Fairy making this Arcanine as a excellent counter and check to Mega Mawile as it resists Play Rough and Iron Head, threatens to cripple with Will-o-wisp, or downright outright attack it with super effective STAB Flare Blitz.
3. With defog buff, hazards are a lot easier to remove so Fire types have a much easier time switching-in.
4. Will-O-Wisp now has a boosted accuracy from 75% to 85% and is a bit easier to rely on and a beautiful move against King's Shield Aegislash.
5. Talonflame's +1 Brave Bird and +1 Roost are difficult to handle, luckily this Arcanine has +2 Extreme Speed and enough bulk to survive a 3HKO from Sharp Beak Brave Bird with intimidate taken into account.
Calcs:
-1 252+ Atk Sharp Beak Talonflame Brave Bird vs. 252 HP / 252+ Def Arcanine: 105-124 (27.34 - 32.29%) -- possible 4HKO
Arcanine makes a really nice pivot pokemon as it resist's both of Scizor's STABS and doesn't really care if it has Swords Dance or Choice Band. It is one of the best counters and checks to Mega Mawile as mentioned. Intimidate is always a fantastic ability to have on a pivot pokemon like Arcanine and really helps ease the tension of offensive Juggernaughts like Mega Kangaskhan. Will-o-wisp is the icing on the cake as it can cripple any physical attacker both on the field or on the switch and then proceed to recover the lost HP with morning sun. It has utility in Will-o-wisp, recovery in Morning Sun, +2 Priority in Extreme Speed and a strong STAB in Flare Blitz.