Goofball, when one departs from the rules of grammar using a sentence fragment, or for that matter, a sentence consisting of only a single word, it is usually for emphasis, but it is essential that the meaning is clear.

It's not a substitute for chronically bad grammar, which usually springs from a combination of ignorance and laziness.

I know you are literature-challenged, but Hemingway did it all the time.

Don Firth