What is the most important project deliverable?

You might think it is the requirements document.

The most important deliverable is the Project Statement of Work. The Project Statement of Work should fully describe the goals and objectives of the project, approach to completing the project, and all deliverables expected to be produced, reviewed and approved. Most projects have difficulties because they are not well conceived. A poor or missing Project Statement of Work is the first symptom of a poorly conceived project.

Here is a Statement of Work template:

Statement of Work (MS Word format)

Statement of Work (PDF format)

Business requirement documents are the next most important deliverables. A project that understands the needs of the business is in a strong position to be successful.