Instructables user “crreed” is an MIT mechanical engineering student that decided to create a full-functional grappling hook launcher based on a NERF N-Strike Raider Rapid Fire CS 35. More information. Video after the break.
The list of things you need for this build is long, but major parts are a dry chemical fire extinguisher, copper pipe, hose clamps, blowgun, and a 20-ounce CO2 canister.
[via Technabob]