I think AP Nunu is actually pretty fun in lane. His iceball is a 1.0 ratio, his ultimate is also realllyy strong with AP, he has more sustain than most casters with his consume. BUT he only works really well if the other team is severely lacking in disrupts. If the other team has no solid disrupts, or they constantly get baited into fighting in brushes, AP Nunu can be devastating.
Tank Nunu is whatever. He has slows, his ultimate slows movement and AS, he has a nice team mate buff. So if the other team is heavily reliant on movement and AS he can work. But as far his jungle goes it definitely took a massive nerf with his consume and early ganks. And there's just better mid lanes than AP Nunu.