One material not often used by personal 3D printers is Nylon. It's a well-known plastic that can be 3D printed by commercial 3D printers and some personal devices, too. What makes nylon so interesting? It's the strength of the material. Nylon can take quite a bit of stress before breaking.
In a fascinating video by Shapeways creator Magic2002 Nylon material is tested to the breaking point. Magic2002 markets a RC car frame on Shapeways and it's critical to determine whether the frame is able to withstand the stresses of actual RC use.
The test showed that the breaking point of the model was likely far above anything a driver would reasonably experience. Shapeways points out that such testing is essential for anyone attempting to market stress-attracting objects. They'd better not break!