Evansdale Waterfall
This is a great trek through a narrow gorge covered with ferns on either side. The waterfall itself is pristine as not many people go here. I've been a dozen times and never seen anyone around. The waterfall itself isn't massive, but still quite remarkable with a good flow. Also there is a nice pool to have a cold dip in at the bottom.
Directions
From Dunedin, head over the northern motorway towards Waitati. Keep going on State Highway 1 and note when you pass the Glenhouse (Evansdale Hotel). Just over the bridge up the Killmog (That nasty steep hill) 200 meters and then there is a road that veers off to the LEFT. Take that down the gravel road. At the bottom there is a river you can drive through if your game, or just stop before the walking bridge. From here there is a well hidden trail on the other side of the walking bridge. Take that up into the woods, it is very muddy most times of the year. 15 minutes into the forest and you will see the waterfall. Good luck and safe travels.