Oooohhh, there are so many gems to choose from:
Matthew Broderick in WAR GAMES: When the computer asks him at the end of the movie what has he learned? "The only way to win the game, is not to play it"
Dirty Rotten Scoundrels: When Steve Martin is faking a war injury to be taken back to the mansion to compete in the race to scam a rich girl out of her money, the butler looks down on him lying in the back seat of the convertible and says, "Welcome to HELL".
Somewhere in Time: When the elderly Jane Seymore puts a pocketwatch in the hand of young playwrite Christopher Reeve and says mysteriously, "Come back to me".
Down Periscope: When Kelsey Grammer asks his Second in command what he thinks of the new rusty, decrepit submarine they've been assigned to, he says, "I think I need a tetanus shot just looking at it"
Young Frankenstein: As Victor Frankenstein is wedged between the revolving bookcase and the wall, he tells his assistant (Terri Garr) through clenched teeth, "Put...the...candle.... BACK!" to free himself
Young Frankenstein: Victor asks Igor (Marty Feldman) whose brain did he steal? He says, "Someone named Abby...........Abby-normal"
Dances With Wolves: Kevin Costner finds the skeletal remains of a man out in the desert and says, "You know, somebody back east is probably wondering why he don't write....."