there are a few that come to mind
Godfather: Kay (Diane Keaton) asks Michael if he had his brother in law killed, and he says no, she is happy with that and walks out of his office, there is a long shot with her in the foreground preparing a drink, in the backgrond we see a a man kiss Michael's ring and call hi Godfather as the door shuts, the scene closes the camera closes on her face with a look of realization that he just lied to her and the godfather waltz is playing in the background.
Empire Strikes Back : Han Solo placed in the carbon freezing chamber, and of course that wonderful ending, Luke finds out his father is Darth Vader and he gets his hand cut off.
Apocoplypse Now: Martin Sheen's complete mental breakdown in the hotel, and of course when he finally catches up with his target, as he kills him the movie is spliced with cuts of a cow being slaughtered while the Doors' The End is playing in the background.
8 1/2: the final scene when everyone that was in his life is in a circle surrounding him
The Ten Commandments: Charlton Heston plays Moses and he is brought before the Pharoh who always thought it was his son, Moses is in chains and the Pharoah asks him if he is an isrealite and he says yes, as he is escorted out of the building in the background there is a pounding drumbeat and the Pharoah has a great line about whipping out the name of Moses from all the temples in Egypt forever, etc, etc (i am not doing the scene justice)
Touch of Evil: at the end when Quinlen the corrupt detective is killed (played by Orson Welles) is killed by his best friend. He is lying in a pool of water and she is leaving she says "he was some kind of a man" standing next to her is a cop and he says, is that all you have to say about him? She replies "what does it matter what you say about people?"
Casablanca: in Rick's Diner when the Germans are singing a song and all of a sudden a small but ever growing number of people begin singing the french national athem and eventually drown the German singers out.
Star Trek 2 the Wrath if Khan: Kirk is left on the planet and you hear him screaming Kahn.... Kahn..... Kahn...
Odd Couple: Oscar throws a plate fo spaghetti onto the wall and Felix is irate and Felix is about to clean it up and Oscar eventually chases him to the the roof and a great excahnge between two actors is played out.
The Heiress: Morris comes to the door because he thinks he is going to be with his "love" Catherine Sloper (Olivia DeHavilland) but she knows that he is after her money and to return the favor she makes him pound and pound at the door as she finishe knitting, eventually she takes her lantern and goes up the stairs, as she ascends the stairs we can hear Morris screaming and pleading, the shot changes to the outside as we can see throught the two small windows above the door the light slowly fading into the distance (whan an ending)
It's a Mad Mad Mad Mad World : as the man that just had a traffic accident is dying he tells the men surrounding him that he was on his way to uncover a whole lot of money and its under a big "W", after that he dies, or so we think he wakes again only to repeat a big "W" and finally kicks a bucket literally.
I could go on forever, sadly there are so many others that I left out but thats the way it goes i guess. So many great movies, so many great scenes so little time
