9 Game Of Thrones Characters Who Could Defeat The Night King
5. Arya Stark

We don't know the rules of the Faceless Men's abilities, but since her taking Walder Frey's face allowed Maisie Williams to fully transform into David Bradley, we can assume they're fairly lax. And that offers up a possibility for the final season: Arya moving silently through the battlefield, disguised as a wight, and takes out the Night King with the Catspaw dagger.
There are a lot of obstacles in the way of that: maybe she can't become a wight, Valyrian steel might not kill the Night King, and he's so powerful and all knowing that he'd probably sense her anyway, while it could lack the dramatic heft of something like a full on duel you'd get with other characters.
But Arya has to have some importance to the endgame, as she's one of the original five characters Martin said would survive, and she's got that Valyrian steel dagger with her too, as well as being a badass fighter/assassin. There's surely a greater purpose to all that beyond Littlefinger's execution, as great as it was.