You can always reference the jQuery object in a variable:

var $el = $('#element');

...then manipulate it.

$el.doSomething();          // call some jQuery methods from the cached object
$el.doSomethingElse();

If the reason you wanted .each() was to reference the DOM element as this, you don't really need the this keyword to do it, you can simply grab the DOM element out of the jQuery object.

var element = $('#element')[0];       // both of these give you the DOM element
var element = $('#element').get(0);   //        at index 0

The two of these are equivalent, and will retrieve the DOM element that would be referenced as this in the .each().

alert( element.tagName );  // alert the tagName property of the DOM element
alert( element.id );       // alert the ID property of the DOM element

I'd note that it isn't necessarily bad to use each to iterate over a single element.

The benefits are that you have easy access to the DOM element, and you can do so in a new scope so you don't clutter the surrounding namespace with variables.

There are other ways to accomplish this as well. Take this example:

(function( $ ) {

    // Inside here, "this" will refer to the DOM element,
    //    and the "$" parameter, will reference the jQuery library.

    alert( this.tagName );

    // Any variables you create inside will not pollute the surrounding 
    //     namespace.

    var someVariable = 'somevalue'; // is local to this function

}).call( $('#element')[0], jQuery );

To directly answer your question, .each() operates normally on element sets of any size including 1.

You can also omit the .each() call completely and just call jQuery methods on $('#element'). Remember that you can chain most if not all jQuery method calls as they return the jQuery object. This even works on multiple elements for the matter, depending on what the methods do.

$('#element').doSomething().doSomethingElse();

If you need to reference the object multiple times, make a variable:

var $elm = $('#element');
$elm.doSomething();
doSomethingElse($elm);

Use first().

each() matches all elements, while first() matches only the first.

There are other selectors too. When you use the id in the selector, you will only get one element. This is the main difference between .element and #element. The first is a class that can be assigned to many elements, while the second is an id that belongs to only (at most) one element.

You can still use each if only one (or 0) element is returned. Also, you can skip each altogether if you want to link an event. You use each when you want to execute a specific function for each element in the list of elements.