A few years ago I ran through all the realistic emergency scenarios I could think of, living in a large city and driving in a car, and except for "being attacked with a gun" the emergency tool that seemed to be useful in basically every other scenario from a building on fire to stuck in an elevator to being in or coming across a car accident was a tomahawk or an axe with a spike/pick on the other end. They also tend to be cheaper than large axes and so it's easy to toss in the car or leave near the door, etc. It may not be the single best tool for some situations, but it seemed like the best all-around tool for almost every situation.