How to extend jQuery to make it easier to retrieve the tagName

I am looking to extend jQuery so I can easily retrieve the tagName of the first element in a jQuery object. This is what I have come up with, but it doesn't seem to work:

$.fn.tagName = function() {
    return this.each(function() {
        return this.tagName;
    });
}
alert($('#testElement').tagName());

Any ideas what's wrong?

BTW, I'm looking to use this more for testing than in production.