They want to read about what has happened in your life and how it has made you special. Essays based on a challenging experience generally stick in the minds of admissions officers. It was an explanation for leaving a job. It's an example of someone answering the question of what was the most challenging thing that happened on the job. If she hadn't answered with that, she wouldn't have been honest, and she wouldn't have given us the insight she did.
Many students try to distinguish themselves with creative or unusual approaches to their essays.
I've also gotten audio- and videotapes. None of those people are students at Berkeley. It's not a comment on their originality. But if someone is a competitive candidate, he or she usually doesn't spend a lot of time contriving a cute way to present the information. In an otherwise strong application, a nontraditional essay can work.