I remember years ago when I first started with 3D Prototype Design, our lead technician Tim came up with an invention based on FDM printing.
His idea was to make a small hand held device that could be used as a hobby tool to create in mid air random designs. He described it as a sort of glue gun that squirts out plastic (like FDM uses) and as it cooled it would solidify as if in mid-air.
As Tim was one of the first people in Canada to work with the technology way back in ’96 (and 3D Prototype was the first to own and offer FDM services), his hands-on experience with the technology inspired the idea.
Over the years his idea has actually come along (see the 3Doodler above) and is now in the sale bin at the craft store.