Here is another self defense tool that lets you launch darts up to 16 feet. This Ballistic Dart Launcher comes with 6 x 440c stainless steel darts. It weighs only 3.1oz and has a compact design, so you can take it anywhere. It comes with a nylon sheath too.
This ballistic dart launcher has a range of up to 30 feet though it is more accurate at shorter distances. You can find out more here.