Verified answer

Unicorn, dragon, Pegasus, fairy, Phoenix, Griffin

Dragons, unicorns, pegasus, witches, nightmares (I happen to know a nightmare with a grotesque appearance but a beautiful, tender, and loving heart, if that counts. Although I find grotesque appearances to be quite charming due to my current morbid streak), familiars, sirens, ghosts, seers, vampires, werewolves, fairies, pixies, there are really many beautiful creatures...

siren

harpy

witch

technically, if you put characteristics (i.e. color, horns, extra appendages) on a hot guy/girl, you can make any mythological creature beautiful.