Needing to be cut out of my cycling jacket.
I was actually out for a walk, rather than cycling, but I was wearing my waterproof cycling jacket. After a while I was feeling warm, and tried to unzip it. The zip wouldn't go down, although it would go up. After a little while I decided just to carry on with the jacket on.
When I got home I asked my wife to help; she's much better than me with anything mechanical. After more than 20 minutes, trying oil, soap, various tools, she gave up; the zip simply wouldn't budge. So we had to resort to scissors.
The brand (in case you are interested): Madison Stellar. I should say that it has been excellent in every other way for the 18 months that I have had it.