not so much a folktale more of an urban legend, but i like the toilet man that presents two papers and brutally murders you based on the color you pick

but if i had to actually pick a folktale i think nekomatas are cool

Don't know too many, except for the one where a kitty is pawing at a woman and that makes her exit a house that's about to collapse and that's where Maneki-neko kitties are from, i think

I honestly really like the story of okami amaterasu, I heard about it from playing the video game that was inspired by it and it's super cool :o