I believe that houses are the most painted objects in the world. We all care about our house and its looks, that's why we all invest money in the painting and redecoration of the house. I'm pretty sure that guys from https://alextrendpainters.ie/ will agree with me on this, because being more than 10 years in the industry they paint all kinds of objects and houses, no matter the size of it, both small and big. They also offer a comprehensive painting and decorating service which includes wallpapering, commercial property work, internal & external painting and decorating, and much more.
Drawing random doodles probably. Millions of people doodle everyday subconsciously while thinking about something else. Circles, squares, trianges.. Drawing/doodling 3D cubes have always been one of my favourite, since i was a middle school kid and i haven't grown out of it 40 years later
The Fence of Carnegie Mellon University is the most painted object, it was renovated in 1993 when it could collapse under own weight, now is a tradition to paint it)