My favorite in this class was the Phoenix 1000 from US Submarines[1]. As I recall (and someone has worked VERY HARD to scrub nearly every bit of information about US Submarines from the web) they has a really nasty bankruptcy with some very wealthy people upset that they had put down big deposits and ended up with zilch.

[1] https://www.2luxury2.com/phoenix-1000-the-largest-private-un...

[2] https://web.archive.org/web/20111128072852/http://www.ussubm...