A tarp. For actual survival, a generic blue tarp from Lowe’s isn’t going to cut it. I’m looking for something that is specially designed to help you survive in winter, like [the Xenon winter tarp, $140 and the Old Man Winter by Wilderness Logistics, $160]. They can be used as a tent, as ground cover, to catch rainwater, to patch holes, for a trap, and even to drag back heavy animals.
What’s the bare minimum you need to navigate across land?  For most people, that would be a compass and map.  A basic road map is sufficient to get a rough approximation of the lay of the land.  More detailed relief maps can help plan for elevation and estimate possible water sources but they also take up more room in your pack.  Waterproofed or laminated maps are also extremely helpful.  Lensatic compasses are the most reliable for little money.  If possible, a compass and protractor are also extremely helpful for route planning.  Obviously, not as essential but nonetheless useful.

For the Soon to Be Ready for Anything Prepper

The Ultimate List of the 8 Most Important Surviving Skills that will Make the Difference between Life and Death during a Crisis