I’d say just the job i have now. I really had a choice all along (what subject i studied at uni), and had a choice where i applied, so often where you end up working is cause of a choice, which means you can choose a place you think you’d enjoy working.
If I’m brutally honest (which I guess it what you want, right?), it would probably be different.
Don’t get me wrong – my job is great and I get a buzz from working somewhere so sci-fi and which actually does important things. I don’t regret my job and realistically I wouldn’t change it.
…but give a genuinely free choice, I have to stick with an answer I’ve given several times already. I’d be a Mythbuster! I’d get to teach people, I’d get to learn, I’d get to do experiments and build fantastic machines and at the end of the day I’d usually get to blow something up with a totally unnecessary amount of dynamite.