The opera Tosca. The set-up for the death scene is her lover was arrested, tortured, and scheduled to be executed by hanging for treason, but the baron, Scarpia, who ordered it was willing to arrange a fake death if Tosca agreed to sleep with him. She agreed, he organized it so it would be a death by firing squad only they wouldn't use bullets (so her lover, Cavaradossi, just had to fall and play dead, then they were free), and when Scarpia yelled, "Tosca, finally mine!" and went to grab her, she snapped, grabbed a knife, yells, "This is Tosca's kiss!" and stabs him to death while yelling, "Are you choking on your own blood?! Die accursed! Die, die, die!" Once he's dead, she says, "He's dead...now I can forgive him." Then takes the travel pass out of his dead hand and says, "And all of Rome trembled before him."
( http://www.youtube.com/watch?v=Ujwdfdc5ic0 )
Then she went to tell Cavaradossi the plan, and followed to the roof of the castle to watch the execution. The firing squad fires, he goes down, she yells, "What an artist!" and then fakes crying by his side, saying, "Just a bit, be still, don't move..." and then discovers he's really dead--Scarpia had lied and planned to sleep with her and kill Cavaradossi anyway. She's flipping when she hears soldiers approaching and yelling she killed Scarpia. That's where the cool death comes in. As the soldiers come, she jumps on the edge of the roof, yells "Scarpia, (we will meet) before God!" and jumps off.
( http://www.youtube.com/watch?v=tAg3b-WyfOg )
So, yeah. Tosca was kinda badass for an opera heroine.