Smelling Salts is learned by 2 species by level and 12 by egg

Effect, in PokéAPI's words

“If the target is paralyzed, inflicts double damage and cures the paralysis.”

Who learns it

14 species in all, 8 of 14 games shown

Ultra Sun and Ultra Moon: 14 species

Species	Method	Level
Makuhita	Level up	28
Hariyama	Level up	30
Mankey	Egg
Machop	Egg
Lickitung	Egg
Snubbull	Egg
Torchic	Egg
Whismur	Egg
Aron	Egg
Spinda	Egg
Cacnea	Egg
Croagunk	Egg
Timburr	Egg
Mienfoo	Egg

Sun and Moon: 14 species

Species	Method	Level
Makuhita	Level up	28
Hariyama	Level up	30
Mankey	Egg
Machop	Egg
Lickitung	Egg
Snubbull	Egg
Torchic	Egg
Whismur	Egg
Aron	Egg
Spinda	Egg
Cacnea	Egg
Croagunk	Egg
Timburr	Egg
Mienfoo	Egg

Omega Ruby and Alpha Sapphire: 14 species

Species	Method	Level
Makuhita	Level up	28
Hariyama	Level up	30
Mankey	Egg
Machop	Egg
Lickitung	Egg
Snubbull	Egg
Torchic	Egg
Whismur	Egg
Aron	Egg
Spinda	Egg
Cacnea	Egg
Croagunk	Egg
Timburr	Egg
Mienfoo	Egg

X and Y: 14 species

Species	Method	Level
Makuhita	Level up	22
Hariyama	Level up	22
Mankey	Egg
Machop	Egg
Lickitung	Egg
Snubbull	Egg
Torchic	Egg
Whismur	Egg
Aron	Egg
Spinda	Egg
Cacnea	Egg
Croagunk	Egg
Timburr	Egg
Mienfoo	Egg

Black 2 and White 2: 14 species

Species	Method	Level
Makuhita	Level up	22
Hariyama	Level up	22
Mankey	Egg
Machop	Egg
Lickitung	Egg
Snubbull	Egg
Torchic	Egg
Whismur	Egg
Aron	Egg
Spinda	Egg
Cacnea	Egg
Croagunk	Egg
Timburr	Egg
Mienfoo	Egg

Black and White: 14 species

Species	Method	Level
Makuhita	Level up	22
Hariyama	Level up	22
Mankey	Egg
Machop	Egg
Lickitung	Egg
Snubbull	Egg
Torchic	Egg
Whismur	Egg
Aron	Egg
Spinda	Egg
Cacnea	Egg
Croagunk	Egg
Timburr	Egg
Mienfoo	Egg

HeartGold and SoulSilver: 12 species

Species	Method	Level
Makuhita	Level up	22
Hariyama	Level up	22
Mankey	Egg
Machop	Egg
Lickitung	Egg
Snubbull	Egg
Torchic	Egg
Whismur	Egg
Aron	Egg
Spinda	Egg
Cacnea	Egg
Croagunk	Egg

Platinum: 12 species

Species	Method	Level
Makuhita	Level up	22
Hariyama	Level up	22
Mankey	Egg
Machop	Egg
Lickitung	Egg
Snubbull	Egg
Torchic	Egg
Whismur	Egg
Aron	Egg
Spinda	Egg
Cacnea	Egg
Croagunk	Egg

Changed over time

One change since Generation III

1. Through Gen VPower 6070 from X and Y, Generation VI