The unsmiling portraits
A smile 'prettifies' the face, no doubt, but sometimes stripping the face of the mask of a smile allows the viewer to truly see what the face is made of. Because then you can truly look into the eyes. No smiles, no emotions, Just like when the individual is alone, looking at themselves in the mirror, determining who they are before they become who they want to be.
Finally, the facial 'gimmick' that endears us to others. The smile opens up our face, disarms our demeanour and relaxes our viewer. The smile is undoubtedly beautiful, alluring, charming but alas, it is temporary. The smile is probably the best justification for photography if there ever was one.