For Ferrothorn?
+1 252+ Atk Salac Berry Gyarados Natural Gift (100 BP Fighting) vs. 252 HP / 88+ Def Ferrothorn: 234-276 (66.4 - 78.4%) -- guaranteed 2HKO after Leftovers recovery
OK, I guess, but you'd have to hit him on the switch in, you can only use it once, and if you switch in on Knock...