Yup, goto Wanaka.
And you MUST get some Heli-Skiing in. Probaly some of the best heli-skiing in the world.
Um, Snow farm and Snow park are hosts of the NZ freerider ski camp, so I think they have some pretty sick parks and pipes. Never been there myself however.
If you're making the effort to come down here, go to all the fields. Because they are quite small (most don't have more than 10 lifts), you can quite easily cover the whole mountain in a day or two.