Your teeth can make or break your looks. Braces aren't just cosmetic though, they'll help you prevent other dental problems, like gum disease, which can actually lead to heart disease.
Working out isn't vain; it's smart. We get only one body, and we have to live in it every day until we die - might as well take care of it.
On the other hand, spending time in the tanning bed will age your skin prematurely, but men can get away with that more easily than women.