Use Snorlax. If you are lucky, it will have the ability "Thick Fat", effectively reducing the damage of Ice and Fire types to it by half. If you are unlucky, both Snorlaxes will have the ability "Immunity", making it impossible to poison.
With an HP stat of 160 and a Special Defense stat of 110, this nigga will wall any special attack you can throw at him. Watch out for physical attacks though.
Go to:
http://bulbapedia.bulbagarden.net/wiki/TypeSee the colorful thing on the right side of your screen, with the word "Types" over it? The left side of that thing is all the physical attacks, the right will be the special attacks.
This nigga can learn Body Slam, Earthquake, Shadow Ball, Rock Slide (good for ice Pokemon, but weak against water Pokemon which will probably be the ones using Ice attacks).
If you want to get even bulkier, but you also want your friends to hate you and think you are no fun, add a Blissey to your team. With an HP stat of FUCKING 255 and a Special Defense 135, it walls any special attack in the entire game. It also gets Softboiled, which in 2signature4me is Recover. Thunder Wave makes your opponent's Pokemon slow as balls, and Seismic Toss does 60 damage, ignoring it's shitty defense stat. It's Special Attack of 75 isn't great, but on Blissey it's usable, so you have access to Thunderbolt, Ice Beam, and Flamethrower.
Unfortunately, it's worse off against physical attacks than Snorlax, so keep it away from those.
