Shagnasty Labs: steampunk creations and culture, galore!
Party people have been modifying Nerf guns for fantasy fun for quite awhile. Here's a guy who has it dialed in and is cranking them out. $55 gets you a basic souped up classic Maverick. One-off's go on up in price, I imagine.
Check out this laff riot Steaming Mad Englishman rap video: http://www.shagnastylabs.com/funstuff.htm
Don't overlook the amazing fact-fantasy story about the inventor-author's father, a renowned explorer, as he searched for the truth about the Tunguska Event -- a mysterious enormous fireball that exploded over Siberia long ago: http://www.shagnastylabs.com/stories.htm