A spreadsheet with relevant, well-researched SEO keywords that are mapped to each blog topic they belong to.
You clearly see the blog topic, the corresponding keywords, plus numbers telling you how often the keyword is searched and how easy or difficult it is to rank in Google for that keyword.
I also include a summary report that explains the topics I found, why I chose them and other SEO intel I find along the way. This helps you answer any client queries and feel confident that the best topics have been chosen.