I got the 7 figure set with hologram Ironhide and hologram Bumblebee.
The 7th mystery figure in the red box for me was this guy:

As I collect Optimus I'm relieved to have found him without too much expense.
Interesting to know he isn't the unique figure in all the packs. I kind of assumed you'd get the rare Optimus or Megatron...

I still haven't found the Advent calendar yet despite constant searching of the Big W's, K-Marts, Woolworths and Toymates "near" me. Hoping it will be in stock somewhere soon as these little figures are addictively cute!