As a non Australian, I didn't know wittenoom, but I'm pretty sure I know of it from the old videos of asbestos shoveling competitions that went around a few years back.

I think the smallest Australian town I know is oodnadatta, but I don't know why I know it. I also had to look up if "nullarbor" was a city, or just a place name, so idk if that counts.

I reckon Port Arthur is a solid contender with its low population of 251 (known for being the site of a mass shooting that led to significant changes in Australian gun laws). It is fading in name recognition as time goes on though, after all that was approaching 30 years ago and lots of people have been born since then.

My top pick however would be Bega with its population of 5013 and the name recognition the cheese factory has brought. It's hard to go past a name that's printed on cheese (and assorted other products now) in the vast majority of supermarkets across Australia, and they even export overseas to get a bit of international cachet.