I have a rather lopsided smile. I used to dislike it due to my large top front teeth, which stick out just a bit. I like it now though - awkward years can make you self conscious about anything. Due to my overbite, my lower teeth are almost never in photos, unless I'm caught laughing, I guess.
At prom both my date and I ordered posed pics. So they took two. The photographer apparently chose odd moments to click the shutter button. In one of them my mouth was closed, nearly smiling. Not great. In the other, my lopsided smile was caught at an odd moment and I was
snarling. One side was bared in what looked totally like a growl, it was crazy. My date had ended up with the closed mouth shots and did me a wonderful favor by trading with me. Even so, some of my friends demanded copies of the snarling pic instead. Another fantastic high school memory for me.
It's hard not to provide only a Pan-Am smile when dealing with patrons and coworkers, but I think I do a good job of really smiling at people, at least when I'm not having a horrible day. I get some great reactions from people. The more glum they look, the more I smile at them.