I have a jacket that I wear to walk the dog when it's cold, and when I'm shoveling snow. It's wool with some insulation, but it's not particularly bulky. I've had it for seven years or so, and I've worn it a lot, so I wasn't too surprised when I put it on the other day to take the dog out and the zipper tab broke off.
The dog couldn't wait, so when I got back I needed to come up with something I could use to unzip the jacket. I dug around in our junk drawer and came up with a paper clip. I had it on there for a day or so, but the metal was too thin so I switched to a larger paper clip. It works, and the top of the zipper is covered by a flap on the jacket so no one can see it, but I'm still trying to come up with a better, more permanent solution.