When Tatsuo Horiuchi retired, he decided to try his hand at art. But instead of spending money on paints and brushes, Horiuchi used what he already had pre-installed on his computer—Microsoft Excel. Now, the 77-year-old artist is creating remarkably intricate digital masterpieces of the Japanese landscape, all on the free graphing software. (Source)
I have seen some works made using Microsoft Excel for example by coloring cells, but Mr. Horiuchi uses like line tools and bucket tools. The results are amazing.