Ugalla, Kizigo, Muhesi, Moyowosi / Kigosi, Rungwa, Rukwa, Rumanyika, Ibanda, Burigi, Luafi, Usangu, Lukwati, Lukwika and Lumesule. These areas are remote and very difficult to reach unless you want to charter a private aircraft there and back. Road access can take several days, much of which is via poor roads.
Unless you are participating in a hunting safari (Yes – Tanzania allows this!), it is unlikely you will visit any of the places in the list immediately above although it can be arranged. Generally, hunting areas have a low density of wildlife compared to National Parks, but all offer true wilderness, far off the beaten track.