The Grampians are known for their rock climbing, Mt. Aripiles being the most famous. This is real upside down, fingers-in-the-cracks type stuff. There are many more however, and with varying grades. Shown here is another famous climb, though not as steep (by rock climbing standards only) called the Elephants Hide. Here a group of school children tackle the arduous ascent, not far out of Halls Gap.
Another strenuous activity is mountain biking. There are ample steep roads to ease your way up. If you prefer flat roads then there are many of those also, for the less enthusiastic.
Equipment: There is an excellent hire shop in Halls Gap and you can go with organized groups on rock climbing expeditions or biking or just hire and do your own thing.
The rocky Grampians are an ideal and popular place for rock climbing and abseiling.
Here's a pic which was taken on a trip there with work colleagues (I was only an interested spectator!).
The week after the guide who took this group of newcomers to the sport took himself abseiling alone and fell, breaking, quote "almost half the bones in his body" unquote. I guess the moral of the story is, it may be a fun sport, but never abseil alone!
Equipment: You need good boots - the rest of the stuff comes with the fee for the group activity.
Canoeing is another good sport to do at the Grampians on one of the large lakes close to Halls Gap.
Equipment: All gear including life jackets will be supplied.