Part cross bow, part rubber band gun, part cardboard tube rocket, we affectionately refer to this device as the "snake shooter."
You'll need two strong cardboard tubes like the kind that aluminum foil comes on plus one more that fits over the two joined tubes, something like a poster tube might work.
Join the two narrower tubes with masking tape.
Add decorative tape.
Attach rubber band.
Cut notches on the sides of the larger tube segment.
Watch out tube heads!