Calibration print shape
Your calibration shape depends on what you want to calibrate on. Among the most popular:


Benchy as a general "overall" test.
Lattice Cubes for retraction/stringing and overall quality.
Two pillars to test for stringing and temperature/cooling control.
Spikes for retraction, stringing and temperature/cooling control.
Bridges for cooling control. 
Cubes for sizing. They also allow seeing if the printer is skewed in X or Y.
Circles, crosshairs, and squares of just a couple layers high to determine the correct center of the print area and measure sizing.
Cylinders in each other to check the achievable resolution and clearance.
Overhang tests to test just overhangs.
Temperature towers for temperature and overhang.
Impact1 &amp; Bend &amp; Tension test pieces for filament properties - if you have the setups needed.




1 - I couldn't find a proper model for an ISO 148-1 Charpy pendulum impact test in thingieverse