To be struck by a diamond bullet means:
An abrupt or immediate recognition of an idea;
A realization of a big idea that happens almost instantaneously;
Reaching an understanding about a concept or concepts that are very complex and/or extremely difficult to understand;
Moment of clarity;
from "Apocalypse Now" (film by Francis Ford Coppola)
"I've seen the horror. Horrors that you've seen. But you have no right to call me a murderer. You have no right to call me a murderer. You have a right to kill me. You have a right to do that, but you have no right to judge me . It's impossible for words to describe what is necessary to those who do not know what horror means. Horror. Horror has a face, and you must make a friend of horror. Horror and mortal terror are your friends. If they are not, then they are enemies t o be feared. They are truly enemies.
I remember when I was with Special Forces--it seems a thousand centuries ago--we went into a camp to inoculate it. The children. We left the camp after we had inoculated the children for polio, and this old man came running after us, and he was crying. He couldn't see. We went there, and they had come and hacked off every inoculated arm. There they were in a pile--a pile of little arms. And I remember...I...I...I cried, I wept like some grandmother. I wanted to tear my teeth out, I didn't know what I wanted to do. And I want to remember it, I never want to forget. And then I realized--like I was shot...like I was shot with a diamond...a diamond bullet right through my forehead. And I thought, "My God, the genius of that, the genius, the will to do that." Perfect, genuine, complete, crystalline, pure. And then I realized they could stand that--these were not monsters, these were men, trained cadres, these men who fought with their hearts, who have families, who have children, who are filled with love--that they had this strength, the strength to do that. If I had ten divisions of those men, then our troubles here would be over very quickly. You have to have men who are moral and at the same time were able to utilize their primordial instincts to kill without feeling, without passion, without judgment--without judgment. Because it's judgment that defeats us."
~ Colonel Kurtz played by Marlon Brando
“That’s the wonderful about art is that you can have that perspective shift…When I first saw ‘Last Tango in Paris’, it was just about the young woman in it and she was naked…and I didn’t even notice Brando, Brando was not even in the movie. Then I saw it about 10 years later…the woman in it meant a lot less to me…all of a sudden, Brando, I started listening to what he was saying, and I was amazed at what a great actor he was. And some of the stuff sounded really profound and really important and I understood it….When I was forty, I saw ‘Last Tango in Paris again, and every word Brando said was to quote another Brando line, like a diamond bullet. It was like a documentary of the inside of my head, and yeah, the woman was there, but man, everything was there.”
~ Penn Jillette