See the related link below.
Snorlax does not learn hypnosis.
Without hacking, Kadabra cannot learn Hypnosis.
I think Gardevoir is a good Pokemon who learns Hypnosis at level 51
Drowzee and Hypno are top choices. but most psychic Pokemon know/can learn Hypnosis.
Munna and Sigilyph.
Its not a TM. Your Pokemon has to learn it. like Gastly :) (Gengar in lvl 100 with hypnosis is pwnage :p)
you can catch a ralts on route 102 and put an everstone on it, then it will learn hypnosis at level 41
Only certain Pokemon can learn it but you can't find the TM
Munna, the psychic pig, and Musharma, the bigger psychic pig, both learn Hypnosis at quite low levels.
lvl 41
Snorlax does not learn Hypnosis at all. There's no way of doing so except for cheating, not even through breeding.
Hypnosis is not a TM or HM therefor you can not get it but Pokemon can learn it like Hypno, Drowzee, Tangela, Tangroth, and so many Pokemon and their evoulutions