On my honor as a Tully, on my honor as a Stark, LET HIM GO, or I will cut your wife's throat!
Who: Catelyn Stark
Source: Episode 3x9, "The Rains of Castamere"
Note: In the midst of the carnage of the Red Wedding, character siezes Lord Walder Frey's young wife, Joyeuse, and holds her at knifepoint in a desperate attempt to bargain for the life of her son, Robb. Lord Walder casually responds that he'll find another wife, and Roose Bolton delivers the final blow to Robb, stabbing him through the heart. Catelyn then carries out her threat, and stares in horror at her son's body for a moment before her throat is cut in turn by Black Walder Frey.