Favorite Mythological Creature

[Shruikan]

Dragons, obviously. The Vouivre is particular; It's a french wyvern with a gemstone in it's forehead that gives it it's sight. They only remove the stone once a year to bathe, normally Christmas, when everyone's in church and it's safe. Oh and they can also shapeshift into a human form.

Second would have to be the Carbuncle, which as far as I know was made up by Jorge Luis Borges for his Book of Imaginary Beings. It's native to Latin America, and the only known defining feature is that it has a gemstone on it's forehead. If you try to take the gemstone, the Carbuncle can blind you, but if it meets someone who has no desire to take the stone, it will give it to them willingly.
Another thing of note, is that the pokemon Espeon and Carbink are both at least partially based on this creature. :)

Then there's Griffins, which are a bit more famous that the others listed :P