Mmmmmmm, i couldnt pick just one.
- Eucalyptus cameldulensis for their gnarlyness, longevity, big failures, hollows, habitat. And firewood
- Angophora costata for its symmetry in a good example.
- Quercus robor for its toughness, form and longevity.
- Eucalyptus regnans for having been the biggest tree on earth.
- Acer palmatum for its grace and autumn colour.
- Wollemi nobilis for hiding from mankind sucessfully for so many years.
I dunno where to stop, this list could just keep going
