A little box with brackets for making a light source on, for example, a Prusa Boxed.

The box has 5 holes for 5mm High intensity LEDs and space for wiring them and whatever resistors the wiring needs.
The holes are angled up and down to spread the light better.
In my case I wired 2xLED in series with a 330ohm resistor, and another 3xLED in series with a 150ohm resistor. These two blocks were then fed in parallel from 12V.

12V |---LED---LED---LED---150---| GND 12V |-----LED-----LED-----330---| GND

In the end I filled up the entire case with hot glue to make a completely solid part.