This holiday tree ornament can be hung from a tree, or just use it as a simple decoration. Press fit an inexpensive LED light into the top and twist to turn it on or off. Use pliers to spread out the end if needed (see pic). Link below to the LED's I'm using ($17 for 60).
I'm using Green Inland PETG here, but other filaments may also work well.
I print it with my Da Vinci 1.0 (flashed with Repetier Host, sliced with Slic3r).
Settings: This is a solid model, so you'll need to use a Vase Mode. In Slic3r it's called "Spiral Vase" mode, and I use a .3mm layer height, 245C extruder temperature, and a 65C bed temperature.
Interesting note (Slic3r): I've found that increasing extrusion multiplier to 1.75 or even higher in Spiral Vase mode can be a very effective way to increase surface quality and inter-layer strength.