Basically, a child that lives on the street and never grows up. Their ears become pointed, so they always have to cover them up, but they never age and live in the hidden places of the city, foraging for what they need.
Either a Greyhawk aka Steel dragon, (yes, I am a geek) as they spend most of their time in human form, only busting out when they really need to.
Or a Rakshasa- because well- evil Tiger guys? So cool.
A vampire just because with all the vampire fans and Goth wannabees out there, I could probably coast through the rest of my existence without ever having to lift a finger or a fang to get whatever I wanted.
Either a cluricaun or that russian fairy that screams at night and throws onions.
You know my neighbors?
Kitsune would be awesome, they live a hell of a long time (if not forever), and unlike most creatures just get stronger the older they get. I’m not sure if I’d be too keen on carrying out missions for Oinari-okami though. Shapeshifting into a hot chick to lead men to their doom would be a pretty funny gig the first couple dozen times, though.
Either way, I’m afraid I’m probably contractually obligated to say dragon.
I’d go for one of the more Eastern style dragons; extremely powerful, immortal, and capable of taking human form.
Sounds like a wizard.
Does Peter Pan count? Always seemed fun to me.
Alternate, being invisible would be a hoot.
Not a dragon. Cursed with an insaitable lust for useless treasure, and every passing hero or saint wants a piece of you.
Not a leprechaun. I’m not wearing that.
Not a mer-man. Hygiene issues (fish don’t get out to go) and an un-satisfying sex life.
Not a ghost. Hands pass through cake.
Not a sphinx. Guard duty is boring.
Yes, I’m a “cauldron half-empty” kind of guy.
I’d like to be Uncle Arthur. He always seemed to have a good time!
You don’t need to be mythological… one of the running jokes in my old HS group of friends is that Hobbits eat almost as much and as often as Basque and Navarrese do 
(desayuno, almuerzo, aperitivo, comida, merienda, cena, recena* and as many tentempiés as you need; breakfast, mid-morning snack, “appetite opener”, lunch, tea, dinner, re-dinner and as many snacks as needed)
If I had to keep sex, I’d go with a nymph or a sylph (in the most basic “water/air spirit” versions): I’d be able to visit either any place underwater or any place over water/land. Otherwise, there’s some types of duendes which seem interesting (earth spirits, tend to be male).
- in other areas, this word means breakfast; in others, lunch. It can be a confusing word but it’s always a good thing to have.
I thought Puck was a name, not a category?
I’d be a Shadowrun Great Dragon. Able to swap to human form, “treasure hoard” much more likely to be a huge stock portfolio than a pile of gold, and able to be as public or reclusive as I wish.
Shakespeare’s Puck is a distillation of much older english stories about mischievous spirits that developed into brownies, hobgoblins, and Robin Goodfellow.
I’d be a dwarf. You get to play with axes, quaff beer, stay fit by working at forges and mines, quaff beer, work on clever devices, and quaff beer. The bearded women might be weird at first, but I imagine the beer would help.
Did I mention the beer?
You might enjoy being The Librarian, although it must be said that he is not plain.
See, this is why I love this place. Not only are we miles away from Rainbow Unicorn Land, we’re in places I’ve never even heard of. I’ve had to look several of these up to know what they are, and I’m fascinated by everyone’s choices!
I’m surprised that we have so many dragons, though. Wouldn’t it be a lonely life, guarding your treasures in a hollow mountain and hoping not to get an arrow through the weak spot in your scales? I feel like the “dragons that can shift to human form” is sort of cheating, but I suppose if there’s mythological or literary precedent, I’ll have to allow it.
Dragon was my first thought, but I don’t like being alone all the time. Also you’d have to be on the watch for dragon slayers all the time.
I’ll actually go for a Faerie. But not one of those Disney poncing fluttery sparkly buggers, that help widdle lotht childwen; the old Celtic style shapechangers that swap babies for changelings, and lure travellers into swamps.
Cause chaos, shapeshift, fly, and even have your own universe with its own rules to escape to… sign me up! 
That’s what I was thinking. I’ve always had a thing for pegasi: cool, strong, fast, handsome, can fly, can team up with a hero to do great deeds, etc.
A dragon was my very first thought, I admit, but it’s pretty hazardous - you’d always have to be on your guard for some adventurer with a sharp sword and a reputation to earn.