If you want the crag to be close to Halls Gap then probably watchtower. Watchtower is about 3 minutes drive from Halls Gap shops.
Watch tower isn't the biggest crag in the world, but probably had enough routes to keep you busy for a day or two.... Has a couple of sport routes (20-22ish from memory) and several trad routes.
It's not a nice as Summerdays for taking a big group climbing etc....
If you don't mind driving (40mins) you can't beat Summerday Valley for choice, ease and convenience... Flat easy 2 min walk in, really really well made track and area around the base of the cliffs, toilet and the walls are very easy to setup (easy access up and down) and the walls tend to offer a great variety of climbing styles and grades...