Oooh, I have a bunch! Fairytales are fun!
I always liked the Swedish fairytale Prins Hatt under jorden, or Prince Hat underground.
A king who is on his way home stumbles upon a bunch of enchanted leaves that he wants to give to his youngest daughter. The enchanted leaves belongs to Prince Hat, who says the king can have them, if in exchange Prince Hat is given the first living creature the king encounters when he returns home.
Because you all know how fairytales work, of course the first person the king encounter is his daughter, so she goes to Prince Hat. The quirk here is that a.) prince Hat is under a spell that means he cannot allow anyone to see him, so he comes to see her only at night, in the dark. In some versions of the fairytale they have a bunch of kids, in some they don't, but one night the curiosity overwhelms her and she gets a candle and lights it after he has fallen asleep to see what he looks like. Unfortunately, she spills a bit of wax on him, waking him up, and Prince Hat is distraught as his curse takes effect - he is a.) captured by a nasty witch and sometimes b.) blinded. The princess then has to go rescue him by breaking his curse.
It's pretty unusual in that it is a fairytale in which a princess has to rescue a prince, rather than the other way around. It's been a favourite of mine since I was a kid, and read a version of the story in which Prince Hat is a giant bear-like monster most of the time, except for that time when she lights the candle and sees that he is actually a man. It's kinda like Beauty and the Beast, except Prince Hat is never a grumpy-pants to the princess, and she gets to go on a quest and rescue him at the end.
I also like the Russian fairytales of the beautiful Vasilissa, and the one about Ivan Tzarevitch, the Firebird and the Grey Wolf. Russian fairytales tend to be quite... dark? The story of Ivan and the Firebird, at least in the version I read it, contained some quite gruesome dismemberment, and the story of Vasilissa involves her finding her way through the woods with the help of a torch made of a skull with glowing eye-holes on a stick, IIRC.