Probably the best way to do a drop bear would be to stat up a thylacoleo and have 'drop bear' mentioned very quietly as an alternate name for them. According to more recent research they were very dangerous, very heavily built wrestler-type predators that could climb - they'd probably fit the bill nicely.
Other Australian-type stuff - hmm. We've already got megalanias, kangaroos and thylacines. The bunyip has already been done (though imho it was a rather uninspiring adaptation, sadly), min-min lights can just be will'o'the'wisps, and yowies are just variant yetis. Bullockornis (assuming that it's a predator on the paleontologically shaky grounds of 'it's cooler that way') is a terror bird. Many shapechanger-type legendary figures in aboriginal myth can be implemented as animal lords.
Quinkana (the long-legged land crocodile that got named after the above, you might have to call it Baru to avoid confusion!)
The Rainbow Serpent (now THAT'S an epic critter!)
Yara-mya-ya-who (they drink your blood with their tentacles, then eat you, then throw you up later to do it all over again - and again and again until you become one of them)
Perhaps some of the other megafauna like procoptodon or diprotodon
An 'extremely poisonous' simple template! Just to make regular snakes, spiders, jellyfish etc more interesting... ;)