It is from a movie, Army of Darkness, in it the main character gets attacked by a creature and he shoots them with a shotgun, he then tells the virtues of buying a shotgun and then says;
http://boards.rennlist.com/lfupload/S-MART2.WAV

All a play on K-Mart, who we all know if they had been pro-gun would never have gone into bankruptcy.
<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />