I was going to do a BFR in a customer's own aircraft. I had never been in it before. Our friendly POI (no joke, he was a good guy) suggested having a very thourough look through the logbooks as well as doing my own preflight on the aircraft. Glad I did. Last annual signoff was 5 years prior and one of the elevator hinges were completely broken.
In the 121 world, worst I've found is a tire that was flatspotted pretty bad.