The "LifeHammer" is a small tool designed for expediting your exit from a car after a crash. The heavy steel hammer points are for knocking out the side windows to make an exit, while the small hook with a razor on the other end can cut through a seat belt. They're available at hardware stores and on Amazon for around $12 or so.
The LifeHammer was suggested from a Reddit commenter after a story about a truck driver who drove into a lake and survived by remembering that the best time to try to escape a vehicle that's underwater is after it has filled with water, as the pressure between the inside and outside is equalized, making it possible to open the door. That would be a harrowing wait, especially if you were sinking as you waited, but that's good to know.
Also, I know that these sorts of things are best placed in a handy location that never moves, but I can't help but think that with just a little work these things could double as a decent ice scraper.
Previously: IceDozer Plus Scraper [BBG]