Saw this great new flexible filament by NinjaFlex.  Many 3D parts feel rigid and brittle, but there are so many applications that call for flexibility.  Some examples I can think of are cases for phones, kids toys, clothing and things like gaskets on the industrial side.  Our world is made up of objects of many materials from wood to plastic to glass to stone to steel to rubber and if 3D printing is to be a potential complete next generation manufacturing technology it must be able to work them all.  If you need a 3D Gumby file, here you go!