The wall I had the most trouble with in my years of competitive battle is (embarrassingly) a Snorlax. I came across a Lugia-Snorlax combination one day during my Double Battles. I took Lugia down with ease, but... Snorlax managed to obliterate my team somehow... O.O
Now, this big guy has a lot of base Attack and Special Defense, but a lower Defense. That's ok, however, because of its huge HP stat. Snorlax has managed to wall my team because I was lacking strong Fighting-type attacks.
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EVs: 252 HP/4 ATK/252 SP DEF
Ability: Thick Fat
Nature: Careful
-Body Slam
-Earthquake
-Pursuit
-Rock Slide
This set takes advantage of Snorlax's tremendous Special Defense and increases it with the Assault Vest, while sacrificing the option of status moves. Thick Fat boosts resistance to Fire- and Ice-type moves. Body Slam gains a STAB boost and has a chance to paralyze. Also, according to bulbapedia, if the target has used Minimize, it will never miss and will have its base power doubled. Earthquake and Rock Slide are just another couple of powerful physical moves to take advantage of Snorlax's good Attack. Pursuit can clip enemies trying to escape to their trainer while going for another pokemon that might be better suited for dealing with a Snorlax.
Be warned that this set doesn't allow it to heal, unless another pokemon passes wish or something like that.
You could also use this:
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EVs: 144 HP/188 DEF/176 SP DEF
Ability: Thick Fat
Nature: Careful
-Rest
-Sleep Talk
-Body Slam
-Whirlwind
This is more of a harassing set, constantly switching out enemies with Whirlwind, while using Rest to recover HP and using Sleep Talk to keep up with your moves.
Now, for a rapid spinner... I would think Starmie. Starmie was made for a rapid spinning set, with a base Speed of 115 and decent stats the rest of the way. Starmie is a good way to keep entry hazards out of the way.
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EVs: 252 SP ATK/252 SPEED/4 SP DEF
Ability: Natural Cure
Nature: Timid
-Rapid Spin
-Scald
-Psyshock
-Ice Beam/Thunder Bolt
Some people put Surf over Scald, but I like the chance to burn better than flooding the whole field. Psyshock provides Starmie with an alternative to Special Attacks, as damage is calculated by using Starmie's Special Attack and the target's defense.
Basically, it's a physical attack for Starmie that takes advantage of a good Special Attack. That's why it would be preferred over Psychic, which has more base power. Ice Beam and Thunder Bolt are there just to balance type matchups.