My favorite was when many years ago I was sitting in F on a USAir Shuttle from LGA-DCA and then Senator Joe Biden went walking by to coach. My second favorite, and it was all I could do to not interject my opinion on this one, was when I heard two guys sitting across from me in coach on a DCA-LGA shuttle complaining to the FA that their employer, Goldman Sachs I believe, wouldn't let them fly in first because it would look bad after the very recent 2008 financial crisis and bail out.

Other people I have seen in coach on the shuttle that are famous, and in some cases rich, have been:

Chuck Schumer
Placido Domingo
Robert McNamara
William F. Buckley

People I have seen in business on long haul flights when first was available:

Kyle MacLachlan - LAX-JFK
Maggie Gyllenhaal - LAX-JFK
Robert Plant - JFK-LHR

Probably forgetting some. Plant had his whole band in business with him (no, not that band) which I thought was nice. As opposed to Harvey Weinstein who was in first (LAX-JFK) while his assistant was further back. I didn't see how far back. With what we have learned since, she might have tried for the last row of coach.