I was a bit late to vote (I would have cast for Stall-based Balance) but whatever, it wouldn't have mattered. Hippowdon, the best physical wall in the game is still an excellent partner for CB Aggron due to the Sandstorm. With Earthquake and Ice Fang (since we're not going stall, we don't need Roar) it takes care of Pokemon such as Salamence, Gliscor, Lucario, Physical Infernape, and Flygon, all of whom give us trouble. Hippowdon, with its not-so-bad SDef can also check threats such as SpecsJolt, forcing the use of Ice-type moves which Aggron can easily enter on before proceeding to wreck havoc with Ice Fang.
Hippowdon (M) @ Leftovers
Ability: Sand Stream
EVs: 252 HP/252 Def/6 SDef
Impish nature (+Def, -SAtk)
- Slack Off
- Stealth Rock
- Earthquake
- Ice Fang
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Hell, we might even want to try Body Slam for paralysis support over Ice Fang, though I don't recommend it. The point is that Hippowdon checks many of Aggron's nemeses, gives it a boost with Sandstorm, and opens up interesting tactical possibilities (SpecsJolt is only one example).
Hippowdon (M) @ Leftovers
Ability: Sand Stream
EVs: 252 HP/252 Def/6 SDef
Impish nature (+Def, -SAtk)
- Slack Off
- Stealth Rock
- Earthquake
- Ice Fang
---
Hell, we might even want to try Body Slam for paralysis support over Ice Fang, though I don't recommend it. The point is that Hippowdon checks many of Aggron's nemeses, gives it a boost with Sandstorm, and opens up interesting tactical possibilities (SpecsJolt is only one example).