Small and simple Blow gun/Dart gun,east to make and cost free.
Really not much to it only 1 part intructable quick and simple fun and costless.
Collect 2 Old Pens and remove the insides,make sure they slot/connect to each other easily,one slightly inside the other,to make the barrel longer,and loading more easy,find an old container about half the length of a toothpick/cocktail stick i used a film cannister.
How to make the darts Cut half a cocktail/toothpick stick in half,now collect some 3 twine string,and unpick the thread on it,now grab some super glue and glue several pieces of Cut thread to the blunt end of the stick,and leave to dry in a piece of tack for a while,then just pop it into the front end of your blowpipe and connect it up and try it out.
Step 2: Play With It and Test It Out
Make different kinds of ammo and darts experiment till you find what string and dart works best for you.
Might try using a tiny bit of tissue as wadding to increase the range.