Seatbelt cutter & Window breaker, the two in one tool is small but powerful. It can save your life in dangerous situations when you need to leave the vehicle immediately, such as if the vehicle is in an accident.
Non-lethal: It cannot be used to hurt others (or yourself) due to the placement of the blade that prevents anything but a flat seatbelt to go through. This allows you to carry it to most places!
If you drive a car, or travel, seatbelt cutters should be your best buddy, the safety item that you carry with you everywhere you go!
Can you actually bring it with you on board an aircraft though?
It is risky. There is a blade, it could get detected and taken away, but there is no firm statement saying seatbelt cutters cannot be brought on board. So, best option is to leave it on a checked luggage, or carryon if you must, but don't be too surprised if it gets taken away. Unlike kubatons, it is not illegal, so there should be no action against you even if security takes it.