IMMOVABLE OBJECT (Aggron) @ Aggronite
Ability: Sturdy
EVs: 252 Atk / 252 HP / 4 SDef
Adamant Nature
- Stone Edge
- Low Kick/Super Power
- Earthquake/Avalanche
- Thunder Wave/Avalanche/Fire Punch/Heavy Slam/Iron Head
This set allows Mega Aggron counter or check a ton of really dangerous stuff, even when it has a huge type disadvantage. Its raw bulk allows you take a hit and OHKO back, or if you can't OHKO you can can paralyze it with Thunder Wave to stop its sweep, and then deal some damage the next turn.
http://pastebin.com/9wsb9jeY <- bunch of impressive calcs.
In practice though it's not that great because its unevolved form has trouble switching in to stuff it's supposed to stop, and super powerful STAB SE moves are going to 2HKO so it can have trouble switching in even if it's already mega evolved, but it works pretty well as an emergency button because it can beat a majority of physical attackers 1v1, or at least paralyze them. You can even run a wish passer, since Mega Aggron can switch into most non-SE attacks and take less than 25%; Sylveon is a good partner since Mega Aggron resists steel and is immune to poison, while Sylveon resists fighting. Chansey is also good because its wishes are a lot bigger and are guaranteed to heal Aggron to full health, and special attacks, which Aggron struggles again, don't work on her.
You can also run an Autotomize set and try to sweep, but it's not that effective; 140 attack with no boosting item is not that great, especially when your only STAB move is steel which has poor coverage. Pretty much any physical wall is going to beat you, even if you have a SE move that's not heavy slam (Mandibuzz for example doesn't give a fuck about non-STAB Stone Edge.)
