Catlins

Having now spent all of 24 hours in the south east region of the South Island, AKA The Catlin's I can understand the interest.
This is a very remote and unique part of the country.  Intensive farming seems to merge seamlessly with stands of native bush, Penguin nests and other native wildlife.
You need to get off the already remote road to really find the areas little gems but places such as Nugget Point, Purakaunui Falls, Slope Point and Curio Bay make it worthwhile.   My quick rundown on the highlights (that I saw):

Nugget Point - a brisk 900m walk takes you from the car park to a lighthouse (built 1869) with stunning views of the surrounding ocean.  Great wildlife viewing including seals and penguins. Nearby there is another short walk taking you to a viewing area for more Penguins.

Purakaunui Falls - just a short 10 minutes walk from the road on a well formed pathway brings you to the beautiful falls which cascade 20 metres over three distinct tiers.  Photo's of these falls turn up in most publicity for this area, for good reason.

Slope Point - A bit of a walk over private farm land (15-20 minutes) brings you to the southernmost point of the South Island.  For those of you who have been to lands end in the UK, well this is the exact opposite in just about every way imaginable.  Remote, rugged, windswept and awesome, worth the walk!

Curio Bay Fossilised Forest.  Can only be viewed at low tide so a bit of luck has to be on your side but a fairly large area (some 20kms long) of fossilised forest is to be found here.

Accommodation can be found throughout the whole Catlin's region. Most is of the farmstay, B&B or small motel style.

When planing your New Zealand vacation if you don't like crowds and enjoy visiting the more remote and less explored parts of a country then you can't go wrong visiting the Catlin's.