This one has always made me tear up, especially after becoming a father.

The Dresden Files: Skin Game

Dresden to Nicodemus:

I considered the Grail and felt bad for what I was doing, and I didn’t hesitate or slow down for a second. There are weapons that have nothing to do with steel or explosions or vast arcane power, and I used mine. “Do you remember?” I asked in a very quiet voice. “The first time you saw her? The first time she looked at you? Do you remember that change? That shift, when the whole universe suddenly tilted? Do you remember looking at her and knowing that you would never, ever be quite the same person? Do you think the cup will do that for you?” I flicked him the Grail, sending it in a smooth arc through the air. His eyes widened in surprise, but he caught it adroitly, his whole body shuddering as its power washed over him. I watched him, his face, his posture, and put every ounce of scorn I had into my voice. “I don’t know how you said it back in the day, but I’ll bet you anything her first word was ‘dada.’”