Just saw the new Cohen Brothers film "No Country For Old Men".
http://www.nocountryforoldmen-themovie.com/
http://www.apple.com/trailers/miramax/nocountryforoldmen/trailer/
http://en.wikipedia.org/wiki/No_Country_for_Old_Men_(film)
This is a cool gun movie with several scenes of an assassin with a home made silenced 12-guage shotgun. He pumps slugs through the shotgun at long range and buckshot in close quarters. The sound effects seem realistic for the gun with satisfying thuds when the rounds make impact.
Llewelyn Moss (Josh Brolin), a man out hunting antelope near the Rio Grande, comes across a drug deal gone sour and takes a Heckler & Koch SP-89 and extra magazine from a dying drug dealer. There are several prominent shots of the SP-89. You can clearly see the S - F selector switch.
One problem, the story takes place in 1980 as evidenced by the headstone in a funeral scene later in the movie. Did the SP-89 exist in 1980? (edit: The SP-89 was made 1990-1993 so either the movie is historically inaccurate or the Mexican came from the future.)
Pictures I've found:
You can just barely see the SP-89 strapped on him in the picture above.