Show the username of whos logged in?

I managed to put the username in like this:

<?php
global $current_user;
if ( isset($current_user) ) {
    echo $current_user->user_login;
}
?>Here is a nice example I came up with.

<?php  if (is_user_logged_in()){
global $current_user; get_currentuserinfo();
echo('Welcome, ' . $current_user->user_firstname . ' | ');
}
else {
echo "Welcome, Visitor | ";
};
?>

The user_firstname can be changed to a number of things. See:Function_Reference/wp_get_current_user