Sun's Logo
I've always appreciated Sun's logo with its four interleaved copies of the word Sun. According to the WikiPedia Sun's logo, was designed by professor Vaughan Pratt, of Stanford University. The initial version of the logo was shown with its sides oriented horizontally and vertically, but it was subsequently altered to feature the logo appearing to stand on one corner.
The logo is an example of an Ambigram, a calligraphic design that manages to squeeze two different readings into the selfsame set of curves. I first encountered Ambigrams in the writings of Douglas Hoffstadter. I eventually found the definitive work of Ambigrams called Inversions by Scott Kim. Mr. Kim is a master of this art form. He maintains an online gallery of some of his work. It is worth checking out.
The ambigram is to writing as the fugue is to music.