My answer to the question on Quora:
On the assumption that ‘best’ infers design excellence, then I’d suggest some buildings featuring Corten by fellow Aussie architects – Wood Marsh and Nonda Katsalidis.
Australian Centre for Contemporary Art, Melbourne (1998) by Wood Marsh
MONA Museum, Hobart (2011) by Fender Katsalidis
and a (relative) oldie but a goodie:
Beach House at St. Andrews (1992) by Nonda Katsalidis