"Growing up" is overrated. I wish I had gone the musician route instead of IT. The executive career path I've been on pays better, but musician is far more fun. I'm slowly changing my direction.
Oh, and I guess as a direct answer to the question, I started out as a kid wanting to be a pilot, and a later a cop. I turned down a scholarship for an aviation program, which was really stupid of me, and joined the Army instead. At that point I was leaning toward cop, and being in the Army made me realize how much I hated authority so that career idea was out the window. That's when I got into IT.