If anyone has been around knex guns for any period of time, you'll notice there are an amazing amount of misnaming going on. For instance, just because something has a pump does not make it a shotgun! A shotgun is a gun that fires little pellets of ammunition called shot. After looking at all the supposed knex "shotguns", I only found very few that actually fired shot. So I set out to make my own, and this is the result:
A true, pump action shotgun that fires three green rods at a time from a shell.
EDIT: Now an instructable