What are the applications of assembly language?

Answer 1

Microcontrollers might be an application. Also, if we were 30-40 years ago programming videogames (Prince of Persia was developed in assembly).
Assembly language is the closest one to machine language. It is not machine language, but almost.
Also, assembly might be useful when you need very high performance in very specific tasks. Middle-level languages like C or C++ allow you to introduce snippets of assembly code in its code.