Clivia

Long-time favourite of mine, I thought I must've Blipped at least one Clivia before today. Had to go back through all 104 previous Blips to confirm that I hadn't. Mildly surprising, that.
These days, there's quite a slew of them sitting under the Spotted Gum deck that wraps around two sides of the house. They clearly like it there - mostly shaded, protected from the wind, and almost zero plant competitors nearby - because a few years ago there were only a few of them.
I know you can split them, or even grow them from seed (if you know how, and you have the patience), but I now know from direct experience that if you set them up well initially, give them a bit of water and the odd dollop of TLC, and keep them free from really bad frosts - thank you, overhead decking - they will quite happily quietly reproduce themselves and develop into a sturdy little Clivia settlement. All members of which seem to be equally happy with the environment they've settled in to.
Its unfailing habit of flowering in the depths of winter - profusely and brilliantly - is the only trick of any note it has. But what a hell of a trick that is! 
Every other plant all around the place has totally given up the ghost, thoroughly exhausted from their strenuous growing and flowering efforts throughout the summer and autumn. But that's precisely the time the Clivias gird their loins, hoist their skirts, and go hell for leather on an all-in,  two-seasons-in-one super growth spurt.
They maybe relatively slow-growing plants, and their flowers are only in full bloom for one season out of four, but when they are, they have the winter garden stage all to themselves.