I have visited many beaches in New Zealand and was most impressed by Pokohino Beach. I stumbled upon it on Google Maps, and although it takes some effort to get there, it is definitely worth it!
The drive is about 20 to 30 minutes on a gravel road. You need a sturdy car, but not necessarily a 4WD. From the car park, it's a 10 to 20 minute walk down a forest track that is a bit steep and uneven. I would say moderate in difficulty. The extra effort keeps the crowds away and makes arriving feel even more rewarding.