The most recent one I have was not in English. It was a translation question of a slang word between two non-English languages. It failed miserably (just made up some complete nonsense). Google had no trouble finding relevant pages or images for that word (without any extra prompt), so it was rather unique and not that obscure. Disclaimer: I'm not using any extra prompts like "don't make shit up and just tell me you don't know".

Most recent technical I can remember (and now would be a good time to have the actual prompt) was that I asked whether MySQL has a way to run UPDATE without waiting for lock. Basically ignore rows that are locked. It (Sonnet 4 IIRC) answered of course and gave me an invalid query in the form of `UDPATE ... SKIP LOCKED`;

I can't imagine what damage this does if people are using it for questions they don't/can't verify. Programming is relatively safe in this regard.

But as I noted in my other reply, there will be a bias on my side, as I probably disregard questions that I know how to easily find answers to. That's not something I'd applaud AI for.