For me it was Canned Heat at the Port Hotel, in Carnarvon with about 150 other fishermen and women of course,one wild night
Pink Floyd in '86 or '87 at East Freo oval for me.
I could hear them from my house and did a walk up for tickets and loved every minute of the show. Who said pigs can't fly....
that depends on your definition
but the biggest i've ever attended was the Berlin Love Parade in 2000
just . . . . epic !
The concert with the most number of top groups on the one bill I went to was Randwick Racecourse in the early 1970's, during the day/afternoon featuring (in no particular order)
Manfred Mann
Deep Purple
Free
+ supported by Aussie band "Pirahna". What a day!! Got me into music big time......
PS: The Led Zeppelin concert in Sydney was amazing as well & to get a good view as I had to climb a fence and sit on it for the whole (lotta love) time. Worth it. 
