This is the list of families that learn Knock Off in Gen VIII (incl. expected families):
-Machamp, Tentacryel, PJ Fardetch'd, G Farfetch'd, Sirfetch'd, Kingler, Lickitung, Lickilicky, Tangela, Tangrowth, Omastar*, Kabutops*, Shuckle, Ludicolo, Pelipper, Gardevoir, Gallade, Sableye, Crawdaunt...