I purchased one of the higher end Remington units last year. They range from relatively inexpensive "guns" that require a hammer blow to fire the shell, to the one I bought that fires with a trigger pull once the "barrel" is compressed against the nailing surface. No license is required, you can pick them up at just about any hardware store or Home Improvement chain.
By the way...it works great! But it seems every time I need it I have to borrow it back from a neighbor.