Unobtainable for Rising Sun/Waning Moon list.

Formes not available. (Not counting Deoxys and other full on Unobtainables, just alt forms.)

Rattata (forme 0) Alolan Is in
Sandshrew (forme 0) Alolan Is in
Diglet (forme 0) Alolan Is in
Meowth (forme 0) Alolan Is in
Geodude (Forme 0) Alolan Is in
Vulpix (Forme 0) Alolan Is in
Raichu (Forme 0) Alolan Is in
Marowak (Forme 0) Alolan Is in
Exeggutor (Forme 0) Alolan Is in

-Unobtainable atm going by the list-

Charmander/Charmeleon/Charizard
articuno
moltres
mew
mewtwo
Unown
Qwilfish
Mantyke/Mantine
Raikou
Entei
Suicune
Lugia
Ho-Oh
Torchic/Combusken/Blaziken
Mudkip/Marshtomp/Swampert
cacnea/cacturne
Clamperl/Huntail/Gorebyss
Regirock
Regice
Registeel
Latias
Latios
Kyogre
Groudon
Rayquaza
Jirachi
Deoxys
Piplup/Prinplup/Empoleon
Spiritomb
Hippopotas/Hippowdon
Uxie
Mesprit
Azelf
Dialga
Palkia
Heatran
Regigigas
Cresselia
Darkrai
Shaymin
Arceus
Victini
Tepig/Pignite/Emboar
Oshawott/Dewott/Samurott
Munna/Musharna
Blitzle/Zebstrika
Audino
Darumaka/Darmanitan
Maractus
Tirtouga/Carracosta
Archen/Archeops
Ferroseed/Ferrothorn
Stunfisk
Golett/Golurk
Rufflet/Braviary
Tornadus
Thundurus
Reshiram
Zekrom
Landorus
Kyurem
Genesect
Meloetta
Fennekin/Braixen/Delphox
Froakie/Frogadier/Greninja
Spritzee/Aromatisse
Swirlix/Slurpuff
Binacle/Barbaracle
Xerneas
Yveltal
Diancie
Hoopa
Volcanion
Marshadow

Technically obtainable, but limited to 1 or 2 at most. without trading. (not sure about the ubers/ultra beasts as haven't gotten that far in game so they may be obtainable more than once or twice for all I know.)

Zygard (Not in the wild anyways. Obviously obtainable still.) (technically can swap forms at will but still.)

Litten/Torracat/Incineroar (Not in the wild anyways)
Popplio/Brionne/Primarina (Not in the wild anyways)

Type: Null (Not in the wild anyways) (obviously still obtainable.)
Tapu Koko (Not in the wild anyways) (obviously still obtainable.)
Tapu Lele (Not in the wild anyways) (obviously still obtainable.)
Tapu Bulu (Not in the wild anyways) (obviously still obtainable.)
Tapu Fini (Not in the wild anyways) (obviously still obtainable.)
Cosmog/Cosmoem/Solgaleo/Lunala (Not in the wild anyways) (obviously still obtainable.)
Nihilego (Not in the wild anyways) (obviously still obtainable.)
Buzzwole (Not in the wild anyways) (obviously still obtainable.) (actually may not be for Moon. Not sure.)
Pheromosa (Not in the wild anyways) (obviously still obtainable.)
Xurkitree (Not in the wild anyways) (obviously still obtainable.)
Celesteela (Not in the wild anyways) (obviously still obtainable.)
Kartana (Not in the wild anyways) (obviously still obtainable.)
Guzzlord (Not in the wild anyways) (obviously still obtainable.)
Necrozoma (Not in the wild anyways) (obviously still obtainable.)
Magearna (Not in the wild anyways) (obviously still obtainable.) (technically? Event I Guess.)