Sundarbans

Hiron Point
a beautiful spot, great for spotting tigers and other wildlife
Tin Kona Island
another popular spot for wildlife spotting.
Katka
a base for safaris, and good spot to see tigers and for bird-watching.
Dublar Char Island
it's possible to fish here.

For people visiting the place from India West Bengal, the following should form a part of the itinerary:

Sudhanyakhali Watch Tower
Most of the tigers are sighted from this tower. Some other wildlife like axis deers and crocodiles may also be seen from this watch tower.
Sajnekhali Watch Tower
Another watch tower that also houses a museum, a Bonobibi Temple and a crocodile park within its premises.
Sajnekhali Pakiralaya
Dobanki Watch Tower
Bhagbatpur crocodile project
Buridabri
Netidhopani
It has a temple that’s 400 years old
Kanak
Ideal for viewing the Olive Ridley Turtles
Holiday Island
It is famous for the Barking Deers