Broken zippers can rank pretty high on the frustration scale, the more so the farther you are from the stuff you need to make a repair. And once you're back to civilization, the fun is not over, as a broken pull can mean replacing the entire zipper, which is not cheap.
Fixnzip to the rescue! The Fixnzip is a zipper repair system that is about as simple as it gets. Just loosen the spring-loaded thumbscrew until it fits over your zipper teeth, tighten it back up and Bob's your uncle. Use the included lanyard, ring and pull to spiff it up and you're good to go.
The only thing you have to know beforehand is the zipper size, which is usually on the back of the slider. Fixnzip comes in three sizes (and two colors – nickel and graphite) so you can dial it in. I had the medium Fixnzip on hand, which is good for sizes 5-7. Sure enough, it worked perfectly on a size 5 jacket, but was too loose for a size 4 vest.
Fixnzip is the kind of thing that can save a trip, as well as saving a pile of cash on repair costs on your return. It's solid enough to leave on as a permanent solution, and at under ten bucks there is no excuse for not having one in your field repair kit.