If I am doodling, I always doodle eyes. Have for as long as I can remember. The second is hearts, and the third is stars. There is probably some psychological tests somewhere which profiles your personality type based on the shapes that you are attracted to.
At first I thought the question was odd and I don't have a favourite shape. Then I thought about it a bit more and ever since I was little I have doodled cubes. Cubes, cubes, cubes, all over the place, trying to get them perfect. I must be REALLY bad at it . . . it's been over fifty years!! LOL.