I am sure all of you are familiar with this posing “with my lips puckered like that, I think I am sexy but I am not”:

lips

Certainly, I know some guys who think it is sexy, but your humble photographer prefers by far a honest, plain smile:
lips

And forgetting about sexiness, from a photography point of view, dynamism is a healthy dose of fresh air:
lips

Creative Commons LicenseThis work is licensed under a Creative Commons Attribution-Share Alike 3.0 License.