Most dishes from Newari culture are unique to our identity, although I'm not a Newari. We're talking about unique, not what is popular. Cooking a little bit different does not make it unique, concept and the ingredient are crucial. There is not whole lot of things in Nepal for that matter.
Gundrunk is a fermanting/drying concept common among many other Asian countryies, started way earlier than us. Anything from sea weed to spinach can be made into gundruk.
Making  Achar is a simple concept, basically you can make achar of anything. Take a look at the Kim-Chi bar in a korean store. You'll find hundread of different types- their concept of achar. However our spices may be bit different.
Wai Wai is a company from Thailand.
Momo is a steaming concept common in many Asian countries. Chinease call it pot sticker, Japanese call is Gyoja, Russian to all the Istans...they have a similiar concept.
Alcohol---is all over the world. Unique are the those culture who makes them our of honey (Africa and Europe) and trees.

For Nepal:
Newari concept(not the ingredients) of foods are unique like chaatamai, kago, kachela, the momo looking ting stuffed with Haaku(sweets)....to name few.
There are few other ingredient that are unique to Nepal.
Laapsi....what else?
Don't say Timbur....it is common in other countries. Jimbu, if the plant used are truelly from the mountain, is unique but the process of drying/aging is not anything new.

Trivia:
Did you know Indian civilization was introduced to Chiilie by the Portugese...