The Leatherman Signal nabs the top spot when it comes to “Survival” multitools, due to the inclusion of its many outdoor-friendly features. But if overall weight is a consideration, something like the Victorinox Rambler or perhaps the Armbar would be a nice ounce-saving choice.
This wasn’t a quick recommendation, to be honest. I went around for quite a while on whether or not the Signal was a gimmick or genuinely useful backpacking tool. And frankly, I’ve settled somewhere in the middle. The overall toolkit is wonderful, and at least half of the outdoors-focused tools (emergency whistle, sharpening system) work well, though the ferro rod and hammer are less than ideal.
But I’ve genuinely come around on the Signal, and feel that buyers would be well-served by its charms if the weight of something like the Wave+ is out of the question.