Who's the best independent expert/contractor you've worked with?

I'm working on compiling a list of exceptional independent experts who work with startups - the kind who can transform projects or unlock massive value. Not looking for agencies or firms, just independent practitioners who are true masters of their craft E.g. recruiters, lawyers, fractional CXO, advisors, etc.

If you've worked with someone exceptional, please share:

- Their domain/specialty - The specific impact they had - What made them uniquely valuable - Rough price range (if you're comfortable sharing) - How you found them

The goal is to create a resource that helps founders find those rare independent experts who can unlock huge value. I'll compile the responses into a searchable list for the community.