Mwahahahaha... the mighty Aggron. I like using this set, as no one - at all - sees it coming. Go figure.
Aggron (M) @ Weakness Policy/Focus Sash
Trait: Rock Head
EVs: 4 HP / 252 Atk / 252 Spd
Adamant Nature (+Atk, -SAtk)
Automize (Sharply raises your speed! Great set up move with Focus Sash, or if you get a chance)
Iron Head (STAB, accurate, the whole shebang)
Head Smash (Same as Iron Head, except with 150 power. Wow)
Stealth Rock/Earthquake/Superpower (Really up to you here)
Works great in doubles with a Fake Out user to stall the biggest threat while Aggron sets up. He can sometimes take super effective hits to activate Weakness Policy, but fighting or special attacks are a problem. Play him well, and all the shops will be wreaked.