When should you use a functional resume?

Q: When should I use a functional resume?

A: Never.

Why not?

Functional resumes make recruiters think you're trying to hide something, even if you're not.
Functional resumes don't parse easily into applicant tracking systems, which are the databases used at the front end of most recruitment process (and you have to pass through the database, or you won't go on for human review).
Functional resumes make it hard for reviewers to understand your most current skills.
Functional resumes put extra work on the shoulders of recruiters, who usually have to reformat your resume if they want their client (the company doing the hiring) to even consider you.

A sound executive summary that showcases your core value proposition or "so what?" followed by work history (and key details) in reverse chronological order is the absolute way to go with a resume today.

If you've got an incredibly problematic work history, you'll need to use some strategy, of course. Just don't make "functional resume" the heart of that strategy.

Need help? Grab a copy of The Ridiculously Awesome Resume Kit, or consider handing the project right over to me. I write these things for a living, I do.