Remembering the Don't Repeat Yourself mantra, the following apps would be awesome:

• An app that generates a large part of the spec for data-driven applications (i.e. the bit describing all the tables of data) directly from the Django db models defined in Python.
• Similarly, an app that generates UML diagrams from your Django models.

With these in place, part of the functional requirements gathering would be done by writing Python directly. You might have to fix it up a bit to remove syntax errors, but then a few quick commands later and you'd find you had:

• half your spec written
• some pretty UML pictures for management (and a useful reference for developers, of course :-)
• the database structure created
• your data layer written for you by Django's ORM
• a working admin interface
• and a massive headstart on development.

And all this before you come back from talking with the customer! Implementing these apps would be a lot of fun, but I can't justify the time at the moment, seeing as I'm not using Django for any projects like the above. But I can dream...