What it does
Skitter Smack is a Bug-type physical move that always lowers the target's Special Attack by one stage — a guaranteed effect, not a chance.
In doubles that drop is immediately useful: if the foe leans on a special attacker, hitting it with Skitter Smack shrinks that attacker's damage. So one move both deals damage and tags the opposing special output with a minus. Bug hits Grass, Psychic, and Dark for double, and those types show up plenty, so Skitter Smack chips while it weakens.
Folding offense and a debuff into one move is tempo-efficient — you don't spend a separate turn lowering their Special Attack, you do it while attacking.
Who runs it
Araquanid runs Skitter Smack in Champions at 8% usage — a niche set. Araquanid is Water/Bug, so Skitter Smack is a STAB Bug move that also cuts the foe's Special Attack. It's a bulky Pokémon, and dropping the foe's Special Attack lets it stay on the field longer and tank more, because the incoming special damage is lower. Whether you run it comes down to whether you want that pressure on special attackers.
How to use it
In doubles the best target is the opposing special attacker. Hit it, and its special damage drops a stage for this turn and every turn after, easing pressure on your partner. If the foe has one special attacker and one physical, aim Skitter Smack at the special one for the most value.
Skitter Smack is single-target, not a spread move, so it skips the doubles ×0.75 cut and hits one foe for full. That sets it apart from spread Bug moves — it concentrates both the damage and the Special Attack drop on a single target.
Araquanid is slow, so it usually moves last. That actually guarantees it acts after the foe's special attacker — the drop can't stop that turn's hit, but it pins down every turn after it.
Tips & strategy
The Special Attack drop does nothing to a pure physical target. If the foe is a physical attacker, the debuff is wasted and Skitter Smack is just a Bug hit. Don't burn the drop on a physical attacker.
Covert Cloak blocks the Special Attack drop, but the damage still lands. So into a Covert Cloak holder you only deal the Bug damage and the Special Attack stays put — keep that in mind, don't assume the drop went through.
Abilities like Clear Body and White Smoke prevent stat drops, so Skitter Smack's debuff fizzles against them too, leaving only the damage.