Get email of currently loggedin user

In drupal, you can get the email address of the currently logged in user from Drupal itself. Since the email is snyc'd between CiviCRM and Drupal, no need to get the email from CiviCRM.

global $user;
echo $user->mail;

If you wanted to get an email address from CiviCRM (becuase you wanted a secondary, rather than primary address, for example).

Can someone provide a code sample?