One of my favourite movies is Jerry Maguire. Two lines from this film, "Show me the money" and "You had me at hello"*, are in the American Film Institute's top 100 movie quotes. And below it's Valentine's Day according to Zbeschek and Seamus.

*Full quote:
Jerry Maguire: I love you. You... you complete me. And I just...
Dorothy: Shut up, just shut up. You had me at "hello".