6. Katniss & Peeta's Suicide Pact (The Hunger Games)
Before their encounter with Cato, the rules of the Hunger Games are changed so that two combatants from the same District can be dual-victors, a move made by Seneca Crane in order to quell the rioting taking place in District 11 following Rue's death. So, Cato dies and they're the only two left, at which point Crane cancels the rule and states that there can only be one survivor. In defiance, the pair decide to commit suicide by eating poisonous Nightlock, but before they can, the game is ended and they are both ruled victors. It's an enormously cathartic moment and sets in motion the larger-scale conflict between Katniss and the Capitol which defines the rest of the series.