Today's Nerf Fans only really have two rocket/arrow launchers from the Nerf Brand: The Titan and the Big Bad Bow. But the Big Salvo was one of the baddest arrow launchers of all time. Zachary_LJ linked me this on the Nerf Mods & Reviews chat and I couldn't help but think it could be shared here for all to see. This one is built by Megaman_90 on the Oznerf forum.
Essentially, it turns a Quad Arrow Launcher into an 8-barreled Dart blaster. It's potent and powerful! Check out the writeup on the forum!