Be the best?

I'm watching too much TV, an almost inevitable by-product of not having much work to go for, and little money for doing 'fun' things outside the house.

Two adverts have pretty much dug themselves into my conscious, largely against my will:

1. The F.A.S.T. Stroke awareness adverts
2. Army recruitment ads
   

The second, it's making me, er, think... Is it something I could do? Would want to do?
It'd be a big shift in career, clearly, but would give me structure, a steady income, accommodation, training & development opportunities, a pension... All pretty good things, and things I would value, a lot at the moment...
However things like having to conform and being in a job where I might be required to kill another person (and be at significant risk myself) is probably not something I would actually go for, I have though, been on their website.

But how big a shift could I be prepared for? I've been thinking if I was to change my career, as opposed to picking up work on a 'temporary' basis outside of entertainment, or exploring other options within entertainment.

Could I be a Police Officer? Would I enjoy working in Public Transport? Is there a role for me in Retail? Might I find Ambulance work rewarding? Have I got a hidden passion for Teaching? Am I fit enough to be a Fireman? Really, how boring would I find Accountancy? Is it too late to pursue a career in IT? What would I do on a Building site? Are any of these "Sales Opportunities" genuine?

Most of these are things I've genuinely considered as possibilities in the last couple of months... and none of them have felt right, but conversely very few of them have felt wrong to pursue...
How do I pick which one (or more) to pursue? Do I really want to change career permanently at this stage? Am I even in the right place to decide on a long term change?