People periodically go through the exercise of revising their brand's essence, promise, personality, unique value proposition and other brand positioning elements.
A fun approach to this is to pretend that your brand has died. Now you need to write its obituary, its epitaph, and its eulogy. It's obituary is akin to its elevator speech, while its epitaph is akin to its tagline or slogan. While its eulogy is a more thoughtful, in-depth review of the brand. If you want to go even more in-depth, think about writing a documentary about the life and times of your brand. What was your brand best known for? What was its legacy? At its peak, how did people perceive it? What would you want the brand to be known for? Generally, obituaries, epitaphs and eulogies are all positive.
This could be an exercise for the senior leadership team, the marketing team or all employees.
To get you started (and just for fun), here are some real epitaphs taken from real gravestones: