Hey, I haven't applied to specifically ANU, but I have been accepted to other universities based on extra-curricular activities so this may or may not be of much help. A few examples of work that I and others did to get accepted were:
- Volunteer work (a lot of schools sometimes offer 1 or 2 volunteer offers throughout the year so taking them def helped)
- Peer Mentor
- Subject Mentor
- Tutor for younger students
- Instruments (AMEB)
- Sports outside of school, or if you have competed at a Zone/Regional/National etc level
- Sport coaching younger teams
- Sports refereeing younger teams
- Leadership roles within school like SRC, Vice/Captain, Prefect, House Captain
- Leadership roles within certain clubs like for a specific sport
- Fundraising like at school bake sales, market days
- Paid work experience
- Duke of Ed
- Student exchanges
- Competitions you won/achieved good results in like some sort of art competition
I found I could put in one-off volunteering experiences so if you still have the time to, try asking your school or emailing your city council if you're really stuck. Once again, reiterating that I didn't sign up for specifically ANU, but at least some of these should be applicable. Hope this helps