Kangaroos are certainly my main focus with Night Driving. I also happened to hit one 3 years ago and although it cost me an excess payment, for AAMI the bill came too $1700. The problem with Kangaroos is not that they like to sit in the middle of the road, it's the fact that they often hide in bushes/trees on the side of the road and make a last second jump onto the road just as your passing by. Any area with trees/shrubs close to the side of the road, I now drive slower just in case. I havent had roo problems on main highways where trucks and cars are frequent although I still see road kill on odd occasions so the danger is still there.
Wombats are another animal I keep an eye out for as well as Echinda's, to a lesser extent during the daytime hours, as their spikes can puncture tyres.
Semi Trailers, especially at night, tend to be quite dangerous. Around bends I have seen quite a few cross over the centre lines so I tend to keep quite a way left when passing one. December 13, I was driving back from Gunnedah after a evening lightning chase when I came across a 40km/h roadworks zone. The road ahead had fresh gravel stones put over the road for 1km so I slowed down. Unfortunately a Semi Trailer coming the other way didnt think they needed too and passed at 100km/h. Needless to say I didnt appreciate the 6 new stone chips in my windscreen.
Lastly tyre choice is something I dont take lightly and at the start of every season, like to check how much tread I still have and if low, change to newer tyres. Speaking to a few of your local tyre centres about your car type, your style of driving and what conditions you will often encounter (ie for me this includes 80/20 tar/dirt ratio, heavy rain etc.) you will normally get a good idea of what tyres to purchase (And the better ones arent the cheapest!)