@Akame, your gig at Fort Jackson sounds like it was very physically and mentally gruelling. You have my admiration for going through it without dropping out. Good stuff!
Although nowhere near as physically tolling, my greatest achievement would have to be doing over two years of volunteer work with the Ambulance service here, mainly at First Aid Events and bushfire callouts.
It was an absoloute pleasure helping the community during events such as the AFL (our biggest sport here), community markets, sporting events (motorplex) and more. Working with other paramedics and liaising with other agencies including the Police and DFES (Department of Fire and Emergency Services) was also interesting.
We of course had to learn clinical skills to do slightly more advanced First Aid skills including resuscitation, medication and using the defibrillator.