Stuff like the Bannockburn Killarabbit that you mentioned in the Queenstown thread is definitely the sort of thing I'm looking for -- idiosyncratic products that I might only be able to try in one place.
I'd definitely look at visiting Mussel Inn then. Also, kayaking/camping in the Tasman area is amazing. That time of the year is crazy with tourists but still stunning.
Also, drop Townshend's a line if you think you'll be going past. He's literally a dude in his farmhouse shed making cask ale in the middle of nowhere. He won the Champion NZ brewery title at the major awards a couple of years back.
If you are heading further south, Craftwork in Oamaru (
http://www.craftworkbrewery.co.nz/) are also up to interesting things. Their saisons, when on point, are really great. They have recently built a coolship out of an old shower, and are playing with barrels and spontaneous fermentation. Really lovely, friendly, people whose primary business is bookbinding.
The West Coast used to have a great brewery (West Coast Brewery) but the brewer left and now it's a disaster. If you are in Westport, pop your head in but don't go out of your way to do it. The only other brewery there is Monteiths (unless something has appeared that I don't know of). They are owned by one of the big players and have some "ok" beers but nothing to write home about. When I was 18 I loved their Celtic Red, so they are partly responsible for me getting in to beer before I knew wtf anything was.
In Christchurch, I really like Cassels and Sons, and the Twisted Hop. Both do a lot of cask ales. Cassels has a brewpub which is a good visit for their milk stout on handpump. Twisted Hop has a small pub serving everything on cask, and a bigger restaurant/bar/brewpub which I haven't been to but is apparently really interesting.
Also Pomeroy's Pub is a must do. They have about 20 taps, 4 handpumps, and their own small brewhouse. They also have accomodation.
Christchurch is still a bit of a mess after the earthquakes but finding it's feet and really interesting as a whole. Lots of public art/creative spaces where there was once a skyscraper. Good coffee there too.
I'll have a think about anything else interesting/unique.