Ballistic knives are quite useful when you need to attack a target from a distance. They have been around for a while, but there are certain legal restrictions on owning them in many countries. You could always make a simple ballistic knife using everyday tools. FaZe Trooper has put up a video that shows you how to build such a knife out of a candy dispenser:
Ballistic knives can be very dangerous as they can cause severe injury. As you can see in the above video, they are not particularly difficult to make though.