pick

It's based on Slick, the official CSS selector engine used with MooTools.

Here are some key features of "pick":

Supported selectors:
· By tags
· By ids
· By classes
· By custom pseudo-classes

Supported pseudo-classes:
· :empty
· :first-child
· :last-child
· :only-child
· :first-of-type
· :last-of-type
· :only-of-type
· :disabled
· :checked
· :selected

Requirements:

· JavaScript enabled on client side