Not that this’ll surprise anyone, but it’d be fun to be the Incarnation of Time, from Piers Anthony’s Incarnations of Immortality. Oh, wait… Never mind :).
I always thought your username had a story behind it. I didn’t know it was literal.
To continue my Ender’s Game theme, I want to be the Hegemon.
Not lit, but in SW-I’d be a Jedi in the prequel era, and an intel agent in Wraith Squadron post ROTJ. (But since that’s from the NOVELS, I guess it counts as lit!)
An Elf in Middle Earth. Why not? Elves are beautiful, immortal, wise, they get to live in beautiful Art Nouveau-styled estates AND they have pointed ears. What’s not to love?
A Tayledras in Mercedes Lackey’s Valdemar series. I’d want to live in an ekele and have a bondbird.
Tolkien elf (for reasons listed above).
Death (the office… I’d watch for guns, oh yes.)
Drinker of Souls (I love the name as well as the abilities)
Anne Rice vampire (back in the heyday not modern times)
Bene Gesserit
Q (female version obviously)
Aes Sedai (with handsome warder)
Lolth (for those days when you just gotta be evil)
An Agent from the Matrix.
Q
The Old Testament God (the cool one who smote people- the New Testament God is too wimpy)
A Middle-Earth Elf.
- for many reasons alread mentioned here.
A witch from Lyra’s world in the His Dark Materials series
- get to be very old and wise, but still young-looking and beautiful
- get to have a daimon
- get to fly on cloud pine branches
- get to have a cool name, like Serafina Pekkala
A Herald of Valdemar (this is for the 11-year old in me)
-your own talking horse!! (well, horse-like creature)
Oh man! I forgot one of the best ones!
A Jedi Knight
Oh man, where do I sign up?
Otherwise the Patrician, from the Discworld books. The twelve year old in me is jumping up and down shouting ‘Daine! Daine! You want to be Daine from Tamora Pierce’s Immortals series.’ And y’know, I really do. She can talk to animals, it top notch with a bow, plus she has a baby dragon! Doesn’t get cooler than that.
Dude, this is not the UK Census! 
I wish I could sing and generally be impervious to all influences like Tom Bombadil.
(or his secret identity).
Dude…that’s for girls. (if you are a girl then disregard).
I’m going to go with:
-MI-6 '00 agent
-Hitchhikers Guide Researcher
-CIA Agent (like Clark from Tom Clancy’s books)
-A caucasian Ninja
-Psychotic Wall Street investment banker or lawyer
I want to be Delivev Ormoru.
Or a princess of Damar- maybe one of Harimad’s kids.
Or a Westwind guard or a member of the Black Brotherhood.
I think I’d probably really want to be a hobbit. They don’t get involved in kinslaying or anything involving Morgoth, and they eat all the time.
I think that I would like to be a Spacer from Asimov’s robot series. You get to live for a long time, you don’t have to worry about material needs, and you can devote your life to researching whatever you want.
Short of that, I wouldn’t mind being a wizard on the Discworld. I love big meals.
(a) Obsidian Flutterby is, in fact, of the female persuasion
(b) I believe that you’ve just uttered the precise insult that caused F’lar to go all Yoda on Fax at the beginning of Dragonflight. So watch yourself.
Another contribution: I’m not sure how well I’d do, but I strongly suspect that Conrad from The Cross-Time Engineer enjoys the hell out of his life.
(I’ve been trying to think of somewhere in the world of A Song Of Ice and Fire that I’d actually want to live, and so far I’ve come up short…)
Well, Hitchhiker’s Guide researcher would be a close second, but ever since I discovered the Harry Potter books I have SO had my eye on the History of Magic professorship. It sounds like a fascinating subject, living at Hogwarts would be dead cool, and best of all, I wouldn’t have to do anything to make a better impression on the students than Professor Binns.
As Max pointed out, I am a girl.
And what is that supposed to mean really?
Pern novels are ‘girly’?
I really don’t get that.
Besides, it’s only riding gold dragons that’s girly. All of the others are very predominantly ridden by men.
I think that Forensic Sorcerer would suit me.
Failing that, I’d head for Wolff and apply for a job as a Hunter.
I’d be a Culture Mind. Not in a GSV, as those are generally triumvirates. A GCU.
Or possibly one of the original hundred (and one) in the Red Mars books.
Or a Sleepless! But in a less prejudiced world.
There are Mentats in Dune? I thought that they came out of Anne McCaffrey’s Freedom’s Landing series, though that doesn’t seem to be at quite the same caliber as FilmGeek’s other choices. Gads, I love the Freedom series, but I love it in the same way I love McDonald’s cheeseburgers. It’s not particularly good or inspired, but sometimes I don’t want to have to think when I read, just like sometimes I don’t want to cook when I eat.
Anyway, it’d be awesome to be one of the settlers on Botany. Or a student at Hogwarts. Or the Lady of Avalon from The Mists of Avalon.
But who I’d really like to be would be Polgara from The Belgariad. Several hundred years old but looks thirty, first female student of Aldur, awesome cook, noble and beautiful – yeah, that’d be cool.