:last Selects the last matched element.
Note that :last selects a single element by filtering the current jQuery collection and matching the last element within it.
Additional Notes:
Because :last is a jQuery extension and not part of the CSS specification, queries using 
:last cannot take advantage of the performance boost provided by the native DOM querySelectorAll() method. 
To achieve the best performance when using :last to select elements, first select the elements using a pure CSS selector, then use.filter(":last").

<div>
<span>John,</span>
<span>Karl,</span>
<span>Brandon,</span>
<span>Sam</span>
</div>
<div>
<span>Glen,</span>
<span>Tane,</span>
 
<span>Ralph,</span>
<span>David</span>
</div>
<script>
$("div span:last-child")
.css({color:"red", fontSize:"80%"})
.hover(function () {
$(this).addClass("solast");
}, function () {
$(this).removeClass("solast");
});