I would have become an airline pilot. I would have loved being a long-haul pilot. I wanted to do that when I was young. But I thought the only route in was via the military. Back then that was much more true than it is today. Anyway, I was not accepted into a flight training officer's slot in the service, so I moved on.
In hindsight, I wished I'd better informed myself as to alternative ways to get to this goal. It was my own fault, I did not properly investigate it and made too many assumptions.
All this said, I think I ended up where I'm supposed to be. Other careers always look great - especially when you're having a bad day. But - not to sound corny - but happiness comes from within. You can be a miserable rock star or a happy-as-can-be janitor.