As a little kid, I wanted to be an old maid swimming teacher (I liked to swim and I had no interest in ever getting married).

In grade school I wanted to be an oceanographer, but that wouldn't have worked because I get motion sickness very easily.

In high school I wanted to be a nuclear physicist. I did complete a BS in physics but I wasn't smart enough to do that as a career. So I went to grad school in atmospheric science. Still there, but it may not last much longer as my funding dries up.

I still dream of being a bike mechanic again. It might happen. Other things I'd like to do but probably never will: paleontology (trilobites, stromatolites, etc.), evolutionary biology, glaciology.