Ferrocene

Source:
http://syntekglobalxtremefueltreatment1.wordpress.com/2012/12/23/xtreme-fuel-treatment-effects-of-ferrocene-as-a-gasoline-additive/xftferrocenemolecule/

Why?

The fantastic structure has a beautiful symmetry, which has been used to teach group theory in my class. And I love the process how people eventually solve the puzzle about the structure. X-ray crystallography rocks!—Lei Yang