One of my first major projects that I decided to utilize my first 3D printer for was to build a Crossfire 2, which is a 3D printable quadcopter that I learned about from Make Magazine. The frame of the Crossfire 2 was designed by Mike Bristol (a.k.a. MikeyB on Thingiverse), and the 3D models are available to download for free on Thingiverse (https://www.thingiverse.com/thing:234867). I spent plenty of time researching, order parts, building/wiring, and testing this flying beast. Below is a photo of one of the latest iterations after many rebuilds.
I also built a nice gimbal for my action camera using 3D printed parts found on Thingiverse, shown below. This gimbal attaches to the Crossfire 2 and keeps the camera very stable during flight.
Lastly, here are some photos of earlier iterations of my 3D printed Quadcopter.