Honestly surprised no one has mentioned slowpoke here yet; it’s canon in both the games and the anime that their tails are considered a delicacy.
In terms of byproducts, it’s mentioned in their ‘dex entries that you can drink the tea from sinistea and polteageist’s potentially counterfeit chinaware. I mean, you might get your life force sucked out of your body, but apparently it’s good: high risk, high reward.
As for general edibility, I’d consider the least edible types to be rock, ground, poison, and steel; all of these would either actively kill you via ingestion or would be the equivalent of getting a mouthful of sand at the beach. Fun. The least edible Pokémon would be those that would kill you for even looking in their direction (although that’s kind of a given);
technically, you might be able to eat Arceus, but you’re more likely to get stomped to death for even getting close.
Of course, there are exceptions to this—for example, there may be a way to specially prepare certain Pokémon so that they are, in fact, edible (quilfish would probably be similar to pufferfish preparation in real life).
Broadly speaking, the most edible types would be water, flying, and normal. Normal is a bit of a mixed bag, but flying type is generally made up of birds and water type is generally made up of fish. Most normal types would be technically edible, but the question would lean moreso towards
why would you do that (physically, you could eat an eevee, but
emotionally? Imagine the toll).
Pokémon kind of doesn’t offer much insight into the subject other than implications of Pokémon-based dishes and the occasional offhand ‘dex entry that identifies said Pokémon as food (i.e. bounsweet, farfetch’d). So honestly this is a very broad topic.
This is the only one I’m going to disagree with here, because vanillite is stated to just be made of. Well. Ice. Ice that happens to be suspiciously shaped like a frozen dessert. You could eat one, but it would probably be the equivalent of shoveling snow into your mouth (which means I guess you could make one into a snowcone if you really wanted to?). There are
definitely desserts based off of them, however, probably made from the aforementioned miltank/gogoat milk (or whatever dairy substitute they have in the Pokémon world).
EDIT: Misspelled vanillite, whoops.
