In general, more men and women seem to find dark or olive skin more attractive than pale skin. Perhaps pale skin suggests unhealthiness to many, while darker skin is a sign of health and robustness. Of course, our cultural idea that tanned skin is healthy is slowly changing as the incidence of skin cancer rises. Freckly skin was viewed with more reserve. Women were more likely than men to find freckly faces less attractive.
People feel quite strongly about white, straight teeth.
The main concern is definitely hygiene. Yellow, stained or rotten choppers and the bad breath that might accompany them is for most people a rather unappetizing image. However, I would bet that many people would agree that slightly crooked teeth make a smile interesting and may complete someone's extra special look. But isolating each feature is tricky business. A nose is hardly a nose unless perched atop a pair of lips against a backdrop of smooth skin, bejeweled with eyes and crowned with shiny hair.