A good rescue knife is durable, easy to handle, and versatile. It should have a sturdy blade that can withstand heavy use and a handle that provides a secure grip. The blade should also have a serrated edge for cutting through rope or other materials. A good rescue knife should also have a built-in seatbelt cutter and glass breaker for emergencies. Overall, a good rescue knife is a reliable tool that can be used in various situations, making it an essential tool for rescue professionals.