I'll post mine as a comment.
Far too many times I have shown up to an interview and been expected to know about tech I have never used, nor do I mention on my resume.
Plenty of other times (albeit most often from external recruiters), I have gone into interviews where they apparently wanted only senior developers and within the first 3 minutes been told "you are a lot more junior than we thought."
One time this has kind of worked out for me, but the rest of the time, it was just a waste of everyone's time.
I conducted a behavioral interview with questions that were pre-determined. I thought their answers were pretty bad and felt the 1 hour interview didn't tell me much of what I was looking for. I ended up scoring them pretty low and being over-ridden by my manager as they liked this person.
Turned out that this person got hired and became one of the folks on the team I most liked, respected and got along with. At the same time, their work output had high quality and they were driven.
Lesson: you can't have a confidence of 100% from a 1 hour interview (negative or positive)
My solution is now to have a characterize their performance using a confidence interval. It makes choosing the score much harder, but results in really thinking about grading the candidate in a clearer way.
Where every question they asked me in the phone interview was wrong, and so it wasn’t possible for me to give the “right” answer because it was also wrong?
That slapstick comedy ended when I somehow managed to connect with their Director of HR, and he paid for my lunch while I told him and his assistant everything that was wrong with the approach Rackspace was taking towards hiring. And he agreed with everything I said. A couple months later, and he was gone, too.
At least they haven’t bothered me recently.