Zuruzukin @ Leftovers/Rugged Helmet/Big Root
Impish or Careful 252 HP/252 Def/4 SpDef or 252 HP/252 SpDef/4 Def
Intimidate
--Amnesia
--Drain Punch
--Dragon Tail/Payback/Thunderpunch
--Bulk Up/Substitute/Thunderpunch
This thing is a beast. The physical one only takes 35.3-42.2% from Offensive DD Gyrados's Waterfall. It can also hit back with Thunderpunch, but it can't OHKO (it needs 252 Atk to guarantee a 2HKO against Bulky DD Gyrados at -1). Because Drain Punch got its power raised to 75, it is now superior to Brick Break. This gives Zuruzukin a recovery move, because not only does it hit with STAB, but it also recovers damage. But the real star move in this set is Amnesia. After amnesia, Zuruzukin's SpDef rises to 534 (or 722 if you go with the specially defensive set). This combined with Intimidate makes Zuruzukin both a great physical and special wall. Zuruzukin can use several phazing moves such as Roar or Dragon Tail, and it can also use Bulk Up to further boost its physical Defense and Attack which couples well with Drain Punch. Payback is also really good for taking down many faster threats. Leftovers gives you more recovery, but Rugged Helmet helps it deal more damage to wall breakers. Big Root is gimmicky, but it helps if you really need a stronger recovery move.
Several other things help him become the ultimate tank. He is resistant to SR, which helps him switch in on threats. He is also immune to psychic attacks like Psycho Shock, which every special attacker is going to carry to get past Blissey. He can switch in on any Dark, Psychic, Ghost, or Rock move. Only fighting and flying hit him supereffectively, and flying isn't too common. He automatically lowers the opponent's attack every time he switches in. He is truly an amazing tank.
For the specially defensive set:
Use Careful and max out the Special Defense EVs. You can exchange Intimidate for Shed Skin if you hate status, but sometimes some physical bulk can't hurt either. Amnesia is ridiculous on this set (modest specs Heatran with max SpAtk Fireblast does about 28-34% after +2 Special Defense). Don't use Bulk Up, because you are focusing on SpDef. Thunderpunch is also useless because it is meant for Gyrados.
Impish or Careful 252 HP/252 Def/4 SpDef or 252 HP/252 SpDef/4 Def
Intimidate
--Amnesia
--Drain Punch
--Dragon Tail/Payback/Thunderpunch
--Bulk Up/Substitute/Thunderpunch
This thing is a beast. The physical one only takes 35.3-42.2% from Offensive DD Gyrados's Waterfall. It can also hit back with Thunderpunch, but it can't OHKO (it needs 252 Atk to guarantee a 2HKO against Bulky DD Gyrados at -1). Because Drain Punch got its power raised to 75, it is now superior to Brick Break. This gives Zuruzukin a recovery move, because not only does it hit with STAB, but it also recovers damage. But the real star move in this set is Amnesia. After amnesia, Zuruzukin's SpDef rises to 534 (or 722 if you go with the specially defensive set). This combined with Intimidate makes Zuruzukin both a great physical and special wall. Zuruzukin can use several phazing moves such as Roar or Dragon Tail, and it can also use Bulk Up to further boost its physical Defense and Attack which couples well with Drain Punch. Payback is also really good for taking down many faster threats. Leftovers gives you more recovery, but Rugged Helmet helps it deal more damage to wall breakers. Big Root is gimmicky, but it helps if you really need a stronger recovery move.
Several other things help him become the ultimate tank. He is resistant to SR, which helps him switch in on threats. He is also immune to psychic attacks like Psycho Shock, which every special attacker is going to carry to get past Blissey. He can switch in on any Dark, Psychic, Ghost, or Rock move. Only fighting and flying hit him supereffectively, and flying isn't too common. He automatically lowers the opponent's attack every time he switches in. He is truly an amazing tank.
For the specially defensive set:
Use Careful and max out the Special Defense EVs. You can exchange Intimidate for Shed Skin if you hate status, but sometimes some physical bulk can't hurt either. Amnesia is ridiculous on this set (modest specs Heatran with max SpAtk Fireblast does about 28-34% after +2 Special Defense). Don't use Bulk Up, because you are focusing on SpDef. Thunderpunch is also useless because it is meant for Gyrados.