I personally feel the answer to this would be fairies, but that is me. Let me know what you think are some of the most neglected in literature.

O_O Faeries, are you kidding me? No offence... but they are the subject of centuries worth of literature, not to mention much modern media also!

The hybrids - half human, half supernatural. They're torn between two worlds and two sets of beliefs.

Miss Pleach (Hybrid Extraordinaire!)
Mischief

Probably creatures like Griffins, Cyclops, Minotaur, or many of the mythical Greek creatures.

Greek mythological creatures, unicorns (how many YA books are there on unicorns???)...
I have to agree with fairies a little bit. At least I haven't read to many modern day YA books with them. But I know those books are out there...still, there could be more.

I think fairies aren't over-looked. I've read a ton of newer books about fairies lately.

I think the ancient Egyptian creatures deserve to be not so over-looked.

I know of at least one YA book about a unicorn, and I know of many others in which they are mentioned.

I would say Golems, especially in their old Yiddish form. Also, Al Ghul would be an interesting change, although ghouls do turn up in The Graveyard Book by Neil Gaiman.

I think the Namba Pamba Pah Poozi is the most overlooked creature of all, because nobody has ever seen it, smelled it, touched or even heard of it until now.

And someday, the hoogula (a mythical creature I made up, who is in my book, The Wish Thief), will be so well known it'll be as generic as a werewolf or vampire. Hey, I can dream, can't I?

Absolutely you are allowed to dream. And as for my opinion on the fairy thing, I would just like to see something a little more grown up about fairies....the same with the unicorns too. They've been so much apart of children's lit that I think they deserve a little more attention.

“Absolutely you are allowed to dream. And as for my opinion on the fairy thing, I would just like to see something a little more grown up about fairies....the same with the unicorns too. They've been so much apart of children's lit that I think they deserve a little more attention.”

Read 'Lords and Ladies' by Terry Pratchett.