The Pencil Rocket Dock was my first experience with how great it is to have a 3D printer at home. I had just got a new iPad Pro and a Pencil, and I was thinking that it would look like a SpaceX rocket if placed upright in a table charger.
It took me about 2 1/2 hours from getting the idea until I was holding the first version in my hand at home one evening. Got to love it!
The first version had straight fins. I later refined it to have nicer shaped and more aerodynamic fins curving at the bottom.
The shape itself was pretty straight forward to model, but it took a little fiddling to get the internals correct and accurate to accommodate a charging cable.