Does resonance apply to NO₂⁺?
In the following below, please interpret formal charges as marked below the atom.
$$\ce{O=N=O} \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ce{O\equiv N-O} \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ce{O-N \equiv O} $$
$$\ \ \ \ \ + \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ + \ \ +\ \ - \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ -\ \ +\ \ + $$

The triply charged species are valid resonance forms, but very likely are small contributors.