Arunachal is one of the Largest State in North-East and has a lot to Offer: You want to to go to Kibitoo (East of North East)
Dong Valley - See the First Sunrise of India, Trek in the Midnight
Vijoynagar - Trek for days to reach and Salt is sold here at 200/- KG
Anini - Will take you to the best of Cloudy Roads Depends How much time you have and what attracts you most ?