Building your own flashlight is an excellent way to learn about electricity as well as how to use a variety of tools. Using a 3D printed frame make the process even quicker and easier and results in a nice, polished final project.
Printing the Flash Light
By following the links below, you can access the source file to modify the flashlight frame and insert, or download an stl file for fabrication via a 3D printer. I learned the hard way that it's not a good idea to print more than one frame at a time (otherwise they turn out too brittle and will break when you try to screw on the end cap).
Bill of Materials
Next time I build one of these flashlights, I'm going to try using a brighter LED from Digikey (should be about 3½ times brighter).