I'm not sure whether "proud" is the right adjective, but that batch file I wrote when I was 12 or 13 which moves all images from the Desktop into a folder called "images" has been the single most useful thing I've ever written.
Doesn't have much functional value, but it was easy to write (though over the years it needed some care, mostly thanks to closing weather APIs) and it is a small simple thing I use almost every day, as it is in my autostart.