I made this little gadget in my free time. It is pretty inaccurate and pretty unstable but IT IS A LOT OF FUN!!!!!!!! It can shoot pretty far and fast, and it is almost free to make. The arrows could use some modification to make them more stable but I didn't have the time. Please comment!

Step 1: Getting the Pieces and Materials

Things you will need: all the K'NEX pieces shown, a rubber band (you should get a few so you can test them and see which one fits best), and a skewer (I used a 25cm long bamboo skewer).
You should also get a spotted dark grey rod (K'NEX piece) shown in step 2

Step 2: Making the Main Body

When you have all the pieces together, set aside the orange K'NEX pieces, the rubber band, and the skewer and build this.

Step 3: Making the String (rubber Band)

Now set that aside and loop the rubber bands through the orange pieces as shown (sorry the pics are blurry, my camera doesn't do good close up shots)

Step 4: Connecting the Two Halves

Now attach the orange pieces to the other thing you made, as shown.

Step 5: You're Done!!! YAY!

YAY! you're Done, heres a pic of the finished product

Step 6: Firing

Grab on to the bow just like you would normally, put the end of the skewer on the rubber band, pull back, and fire! WARNING: I am not responsible for any damage you do to anything or anybody. PLEASE do not shoot at anybody even if you really hate them, and don't shoot at anything. Again, I am not responsible for anything you do with this weapon.

THIS THING RRREEEAAALLLYYY HURTS!
IT HURTS RRREEEAAALLLYYY BADLY!!!!!