I wouldn't consider Amoonguss a volt turn counter, because of the reasons you mention concerning Scizor.Just out of interest, I pulled out the Pokémon that are listed for both Scizor and Rotom-W:
Pretty interesting list, but some of these Pokémon definitely couldn't be considered as counters due to being incapable of hitting back. I've picked out a few that I feel could actually do something useful. ;)Amoonguss
Dragonite
Dusclops
Jirachi
Metang
Milotic
Salamence
Shelgon
Tropius
Zapdos
Amoonguss @ Leftovers
Ability: Effect Spore (wish they'd hurry up and release Regenerator...)
Nature: Calm (+SpD, -Atk)
EVs: 252 HP / 40 Def / 216 SpD
- Spore
- Stun Spore
- Giga Drain
- Hidden Power [Fire]
Amoonguss has real potential, in my opinion, thanks to Spore and STAB Giga Drain, which 2HKOs all standard Rotom-W (bulky attacker only after Stealth Rock) while scarfed Rotom-W can only 4HKO after Stealth Rock with HP Fire even before you consider the recovery from Giga Drain.
Choice Band Scizor is a little more problematic, especially if Sleep Clause is active, since U-Turn is a guaranteed 2HKO and Bullet Punch is a guaranteed 2HKO after Stealth Rock. The standard OU Amoonguss set carries HP Ice, but even HP Fire can only manage a 2HKO (61.8% - 73.5%). Against Scizor, Amoonguss' best shot is either waiting until hazards wear it down enough to take it out with a single HP Fire, or catching it on the switch with status.
Defensive Salamence makes me wince. I'm not comfortable with the idea of it, but I will admit you make a point.
Zapdos is only the only perfectly hard volt turn counter in my opinion, and I think the specially defensive set is worth looking into for OU.
Yeah when I read "salamence" at first I didn't think of a defensive set, which threw me off.CB Bullet Punch is a 4HKO with rocks against defensive Salamence after Intimidate. The same Salamence OHKOs with Flamethrower. That's the set that counters Scizor, not the offensive sets which are indeed 2HKOed after rocks and Intimidate.
If nothing else, I run that defensive Mence, and it performs admirably against Scizor.
It's because personally I run a hyper offensive moxie Salamence. Scizor won't stop that thing from sweeping usually, but I guess in a way I can't switch it into anything.