Using very basic tools and cardboard, this is an easy and fun toy to make.
The first step is to look for patterns to use for the rubber band gun. You can either draw them like I did, or you can find it on the internet. You can choose any gun shape you want. After you find some that will work, you can trace them on cardboard. I used a marker to trace the patterns on the cardboard, but you can glue them on and then cut them out which works too.
After we have traced it, we can start cutting the cardboard out and hot gluing it together. You can use a scissors, a utility knife or a scroll saw to cut out the pieces. I used a scroll saw to help cut it out faster. There will be a total of 12 pieces of varying sizes. Four top/bottom pieces (outline of the largest part of the gun), two pieces for the handle, two pieces for the front part of the barrel. Lastly four pieces for the trigger. Two large pieces will be glued together for the middle of the gun. Place the pieces for the butt/handle of the gun together, glue together. Then glue on gun. These will be in the "middle of the gun" when finished. Now place the 2 pieces of the front barrel together and glue together. Glue onto same side of the gun as the butt/handle.
Now that we have hot glued most of it together, we can start making the trigger mechanism. I used small rubber bands (black in picture) to make the trigger snap back in place. Use skewers or toothpicks to keep the pieces in place. Keep skewers in place, do not remove.
Place both large pieces of the gun together, glue together. Now we can glue the last side on to the rest of the gun. Make sure skewers stay in place while you are gluing the last side on. Make holes in the cardboard to allow for easy sliding of the skewers through the cardboard. Cut skewers to thickness of the gun. Glue the skewers in place. Finally cut small groove in front barrel of the gun for the rubber band (about 1/16" to 1/8" inward, small triangle shape). Place rubber band around barrel and stretch towards the back of the barrel. Aim at target and pull the trigger. Have fun!