The most gobsmacking moment I've ever seen from a game show was from a 70's-80's show called "Joker's Wild," in which contestants would pull a 'gambling lever,' and spin three new trivia categories in to slot machine-style windows. Such a cheesy-ass concept, but it was actually kinda cool, and very effective for the day!
You can see a short clip here to give you an idea of what it was like:
https://www.youtube.com/watch?v=UC61NPPiZrA
During a 1972 episode, a contestant spun the category "Annual Events," which was illustrated with a groundhog. The subsequent question was about Groundhog Day, but the contestant pointed out the answer was already visibly depicted on the category slot.
I've seen video of it, and the host of the show, Jack Berry I think? ...lol, simply COULD NOT accept that, like a crooked ref. He did everything he could to wriggle away from the fact that the contestant was not only RIGHT, but pointed out a hilarious flaw in their game design.
Haha, that was a fun show. I used to watch it in the 80's...