In the past (say, LAST YEAR), I used to love carving guns out of cardboard and "finishing" them with colored electrical tape (before the current nanny worries, I used black vinyl tape and silver duct tape).
'Course, I also tried the cardboard with swords, but nothing quite matched the sturdiness of my woodshop Scimitar (or my woodshop rifle).
But this looks like a FUN project: