The earlier phrase to Mick607's above in the same film. Following a gun fight twixt Harry and several accomplices in a shooting exchange outside the local bank, a wounded robber reaches for his spilled weapon. As 'Dirty Harry' stands over him, brandishing his smoking gun, he says;
"I know what your thinking and with all this excitement I don't rightly remember if I fired six shots, or only five? But seeing as this is a Magnum 44, the most powerful handgun in the world and would blow your head clean off, you have to ask yourself one question, do I feel lucky? Well do you punk?"
Deciding against the risk, as he's being formally arrested by the 'mop up' cops, and trolleyed to the ambulance the bleeding gunman growls - 'Hey Man, I's got to know?' Harry grins, holds the gun to his head, presses the trigger and it clicks onto an empty chamber!
Priceless stuff!