I wanted to be a doctor all through my teen years and well into college. Then I flunked organic chem. Twice. 
So I became an English major instead and somehow ended up in student advising. Someday, though, I’m going to write the Great American Novel, I swear…
Then: I wanted to write world-famous videogames.
Now: I want to write world-famous novels.
A science fiction writer. I remember seeing the first Nebula Anthology and thinking, “I want to be able to join SFWA.”
And I have.
In roughly consecutive order:
Astronaut (born 1961, so grew up with the Apollo Program).
Paelentologist.
Marine Biologist.
Oddy enough, I found something in a drawer recently that brought back my childhood instantly: in 1969, I had put together a “museum” in my parent’s TV room one weekend (and was mercenary enough to charge my friends a nickel each admission). In a little blue jewellery box, were two arrowheads (OK, “points”). On the inside of the lid, in my childish scrawl were the words “DO NOT TOUCH!!”
I am now a museum curator. I had completely forgotten about my little Smithsonian, until I found that blue box…
Aesiron: “a professional wrestler or USAF officer…” Why not both? “Colonel Crippler,” or maybe “Major Mayhem?”
Eve, don’t “Bachelorette Pads” come in boxes of 24?
I had a mediocre affair with a Swiss man, does that count?
[Rodd Hill, eww!]
When I was really young I wanted to be a famous gymnast.
Then I grew up a little and decided being a teacher was much more interesting and plausible.
Then I grew up some more and realized that I don’t like to teach, I like to listen. So, I changed my goal to child psychologist.
Then I grew up even more and realized how much I hated going to school (even though I was an honor student) and to become a teacher or psychologist, I would be in school forever.
So, I’m a Real Estate Agent. And I love it! Only went to school for a few months, I don’t sit behind a desk all day, I don’t deal with the same people everyday, and I have no one breathing over my shoulder telling me what to do. It’s the best job ever! 
When I was very young, I wanted to be a police officer. I liked CHiPs, and wanted to be Erik Estrada. I once discussed this with a playmate of mine, who told me he wouldn’t want to be a cop because he might get shot.
And I realized he had a good point.
So, I changed my career aspirations to palaeontologist. I was going to dig up dinosaur bones (OK, fossils)! But then I noticed how a lot of dinosaur bones are in deserts, and that they require working outdoors digging and stuff.
And I thought to myself, I don’t like going out in the hot weather much–I’d rather have an indoors job.
So, I decided I would go with my other childhood passion–astronomy! I wanted to look through telescopes and discover new solar systems. I was actually pretty serious about this idea up until my first year of high school.
And then I encountered algebra. My bad experience with algebra dashed any dreams I had of going into a science field, ever.
With that disillusionment went my last childish dream about my future career. I moved into the humanities (specifically, art history) and have stayed there ever since.
Neither holds much, if any, appeal to me any longer. If I somehow revert to being 12 again, I’ll be sure to remember the suggestion though.
I’ve always wanted to write comic books.
I’m getting closer to this ideal every day, so wish me luck. 
archaeologist, ninja, professional athlete.
Palaeontologist, then writer.
But I’ve settled for sighing over the little models of Burgess Shale fauna at the museum, and doing NaNoWriMo.
[grade five humour]Hee hee hee. Priapulida…[/gfh]
In kindergarten I wanted to be Bank Teller.
In 2nd or 3rd grade I wanted to be an Astronomist.
In 7th or 8th grade, I wanted to be a Rockette.
In High School, I couldn’t decide, though I tossed around Journalist, Nurse, and Teacher.
Starting from when I was about 5 years old:
Author
Fireman
Generic “scientist”
Han Solo (not a spaceship captain; I wanted to be Han Solo)
Astronaut
Author
Director
Animator & director of animated movies
Graphic Artist
Video Journalist
Videogame Designer
Author
Every guy has probably wanted to be a gynaecologist.
Until we realized that not every girl is a super model.
Acck…
I never quite knew what I wanted to be.
I always assumed that there was some cubicle waiting for me at the end of my youth.
And I was right.
But I suppose I’ve always wanted to be someone famous. Actor most likely.
I wanted to be an architect. I would pull the real estate section out of the Sunday paper and spend hours looking at the floor plans in the ads for new homes. I would design and draw house plans all the time.
I kept this aspiration until freshman orientation for college. When I realized how many math classes would be required for an architecture degree, I was intimidated and abandoned that pursuit. I am so not a “math person”.
For a brief time in high school, I flirted with the idea of being a meteorologist. But I am so not a “science person” either. (Meteorology is the only science area I am even remotely interested in.)
I always thought it would be fun to be a park ranger at one of the national parks.
When I was a kid it was an astronaut, probably because we lived close enough to see the space shuttle launches from our yard and it was a major household event.
After I went to space camp I realized that there’s only a few dozen astronauts in a lifetime and maybe I should rethink…
Then in college I wanted to go to medical school to be a plastic surgeon more than anything. That didn’t work out because when I job shadowed a surgeon my body would involuntarily blackout and almost faint during any surgery (that damn smell of burnt flesh from the cauterizer). It also didn’t help that like Emony Dax, chemistry and organic chem. did me in. I like to think that the Straight Dope is at least partially to blame for that (hey, at least I was learning about other neat stuff).
Now I’m on track to go to law school so we’ll see how that works out.
Totally. I’ve never even had an affair with a Canadian…
Your loss. 
A veterinarian. I got as far as college with that one, but I partied a bit too enthusiastically my freshman year and screwed up my GPA.
Oh well.
Now I want to be independently wealthy, but in the meantime I play with computers all day. I love it most of the time, but the job I have now pretty much bites. I’m thankful to have it, but I don’t have to like it.
Ballerina, artist, model, veterinarian, teacher.
Instead, I work with my mother-in-law and six other people who all have full authority to tell me what to do at any given moment. I hope to go back to college one of these days, although I don’t really know what for.
I am also a Mary Kay consultant, and I know I could be doing a whole lot more with it, if only I were organized, disciplined, and focused.