You are quite adventurous. The most adventurous activity I did in NZ was doing the Tongariro crossing. I think I did it in About 8-9 hours. It was a hard climb but the scenery was spectacular.
It was indeed a satisfying experience. There was a lady in the van that took us to the starting point who took a side trip to the crater of Mt Ngauruhoe. She got to the end point less than a hour after I arrived. I thought about going up Ngauruhoe as well but gave up as I was worried that i could not get to the waiting van on time.