We always tell students that sentence fragments are bad, bad, bad. And, if they don't use them strategically, they are. But do you notice how often published authors use them well? What effect does the author create by using fragments?
"This story begins within the walls of a castle, with the birth of a mouse. A small mouse. The last mouse born to his parents and the only one of his litter to be born alive" (Kate DiCamillo, The Tale of Despereaux, 11).
"In the dungeon, there were rats. Large rats. Mean rats" (Kate DiCamillo, The Tale of Despereaux, 25).
"So I wrote a lot of action into my story. I wrote about a bus hurtling down the highway with no one at the wheel. I added a tornado. And a pirate. And a great white shark. But the story didn't seem quite right" (Eileen Spinelli, The Best Story, 4).