I recently made this dart gun , wich can be aslo used as a spitball gun.

Step 1: Tools and Materials

•Electrical Tape (optional)
•Super Glue
•Needles
•Disposable Syringe (I used a 10mL one)
•Q-tips
•Old bic pen
•Scissors

Step 2: Making the Gun

First of all , take apart the bic pen and glue it in the needle adapter. Make sure it's a tight seal to avoid air leaks.

Step 3: Making the Darts

The darts are really easy to make. Take a q-tip and cut it in half. Insert the needle in it and then superglue it. Done ! (I ran out of super glue so I used hot glue wich also works well.)You can also tape the needles on the q-tips instead of glueing them.

Step 4: Shooting It

Now here comes the tricky part.You can either use it as a spitball gun or a dart gun.
If you want to load it and use it as a spitball gun , insert the spitball using a thin wooden stick.
For using it as a dart gun , do the same thing , insert the spitball , and after that the dart. (Make sure you don't do the opposite or else it will only shoot the spitball.)
To shoot it just push really hard on the plunger, and make sure you do it fast.
Have fun !