I've recently stopped doing logos so I can focus on game design. I've designed quite a few inversions for magicians, like Meir Yedid . Some use them on their business cards. I read a news story some years back about an entire font in which every letter inverts. Sounds like a solution in search of a problem, but that didn't stop the inventor from filing for a patent.
Book covers .
For my own book Inversions I created an inversion that turned the title into my name. John Landon did likewise for his lettering book Wordplay. He also created ambigrams scattered throughout the book that figure in the plot. Bilingual signs . The Thai airlines logo looks like it might read in both Thai and English.