Most of ghost pokemons may be used as spin blockers, but I think Shandera Shadow Tag even do more: A spin KILLER!!
Shandera @ Choice Scarf
Nature: Modest
EVs:164 HP/92 Speed/252 Special atk
Moveset:
Flamethrower
Shadowball
Energyball
Psychic
Here is the list of spinner in Black and White:
http://www.serebii.net/attackdex-bw/rapidspin.shtml
With 92 EVs for speed and choice scarf, Shandera is faster than the fastest spinner, Starmie. The moveset above ensure that Shandera hit super effectively ALL spinners in the game, except two NEVERUSED pokemons, Spinda and Torkoal (and personally I think those 2 pokemons would never have a chance to meet a Shadow Tag Shandera in battle, as their power are too different).
Modest nature and 252 EVs brings the special attack of Shandera to sky level, what is even higher than any Timid Mewtwo/Kyogre. With Shadow Tag and the move pool above, there is no way for your opponent to save his spinner, once Shandera is thrown to the field.
Finally, the bases 90 def and 90 special def are quite good, and 164 EVs for HP make this pokemon bulky. With HP invested, Shandera is unlikely to be 1KOed unless hurt by a powerful move that is boosted by both STAB and super effective.
More specifically for most popular spinners nowadays (assume that the spinner only have maximum 87% HP due to entry hazard - as spinning is the reason why they are switched in):
- Flamethrower KO Forretress and Doryuuzu (and bonus for non-spinner Scizor/Skarmony also XD)
- Shadowball KO Starmie and Claydol (bonus non-spinner non-scarf Gengar)
- Energyball KO Donphan and Kabutops (also good for Swampert)
- Psychic KO Hitmontop and hurt Tentacruel