This is one of my all time favourites- instead of a pendulum, this escapement uses a ball bearing rolling along a track to keep time. At the end of the track, the escapement hits a trigger which causes the track to slant the other way, starting the cycle again.
Here is the video that shows how easily this mechanism can be assembled!
The STL File:
Prints on all standard 3d printers without supports, requires the following additional parts to assemble: