Back in agency world (seems like a long time ago...) I never felt right about all the three-ring binders of research, data and "strategy" that was part of the marketing plan we would present with much fanfare, smoke, mirrors and sometimes blazers and mock turtlenecks. I think the idea was to overwhelm the client with volumes of ideas and marketing tactics.
However the one little sliver of work I felt not only "OK" about... but was actually quite proud of was the questionnaire (or equivalent) and the things I would learn from it. Ultimately the work I did came out of this give and take, this relationship-building and deeper understanding.
The deliverables ultimately consisted of a logo, broader identity system and brand guidelines. In other words, the (not-so-small) part that I played as part of this broader engagement was the most valuable part to me (and probably my customers). I loved actually getting to know the client through its founders, the good work they were leading, their compelling story of "why" under the surface and the audience they were trying to reach. Again and again, this is the work I come back to and value most... and will strive to do.