Flapping bat key holder that mounts to the wall with two nails.  The wings work with gravity, so it will be important to print the wings and the key hook with the right infill percentages to get the weights right.  I would suggest high infill for the key hook (>50%), and low infill for the wings (~10%).  I've included the step file if someone wants to remix this with a version that snaps together, or a different way to mount it to the wall!