Here is a simple 3d printed, 3 part LED micro light, small enough to hang on a key-chain.

Step 1: How It Works

A micro flashlight that can be attached to a key-chain can be easily 3d printed.
The LED slides in and out of channels in the case to act as a slide switch to turn it on. A square hole on the side allows a toothpick to be used to push out the 2016 cells when they need replacement.

Step 2: Materials

Ninjaflex filament to print the body of the flashlight. Available from Adafruit: http://www.adafruit.com/products/1691
PLA or ABS will not work, as they are too stiff to provide reliable slide switch action or battery replacement.

White or blue 5mm LED. The leads must be cut to about .4 inches and then bent as seen in the step2 pic.

Battery- 2-cr2026 lithium cells available from hardware stores or mouser.com.

Step 3: Printing the Case

The case was designed using the free program: 123D design.
The case (flashlite.stl) must be printed using Ninjaflex. Other filaments are too stiff to work as a good switch and allow installation of the battery cells.

Details on using Ninjaflex can be found here:

https://www.instructables.com/id/How-To-Use-And-Opt...

Replicator 2 Settings

These settings work well for a Replicator 2. If you use a different printer, you may have to play with the settings.

No supports

Infill: 10 per cent

Shells: 2

Layer Height: .2mm

Temp: 235 C

Speed Extruding: 30 mm/s

Speed Traveling: 150 mm/s