The logo SUN Microsystems had is a 4-way ambigram with rotational symmetries. Designed by Professor Vaughan Pratt of Stanford, the logo features 4 interleaved copies of the word "sun", forming a rotationally symmetric ambigram, with the letters U and N in each word forming the letter S for the next word.
You can read the word "sun" if you rotate your head by 45°, 135°, 225°, or 315°.
* Objectively according to me. :P