Sirens, specially the Loreley. Though dragons are awesome too. As are vampires, but that's more because my dad comes from Transsylvania (but he's more of a werewolf). Did you know that Butterflys are named that way because they were accused of making butter out of milk? German Elves (those guys that sit on your chest while you're asleep, suffocating you and causing nightmares) are an interesting bunch, too.
I personally like mermaids because well, let's say that I'm like a silly little cat that is fascinated with water. And I always found water creatures to be mysterious and beautiful and sometimes deadly as well :3 So calming too~ Mermaids really entrance me. Mermaids aren't the only water creature I like, I like kelpies too and I also like sea nymphs and nereids and such and such :3 I have an original character that is a Nereid x3333
To tell you frankly I like all the creatures for different reasons. :3