So many to choose from...
One that happened to me a few years ago. I'm at my local range on a lane with no one to the left of me in the next two or more lanes. A young guy shows up with his girlfriend who is unfamiliar with guns. He takes the lane two to my left and she takes the one to my immediate left. He gives her some basic firearms safety instruction and then hands her his mom's old 25 ACP. He shows her how to load it and tells her it has feed issues. She'll have to rack the slide manually every time.
So she takes aim, fires, and then brings the gun up so it's pointing straight up. Her boyfriend congratulates her and encourages her. She seems pleased. Up to this point, everything is a-okay. He then tells her she'll have to rack the slide to feed the next shot in. So what does she do? She tilts the gun to her right, so that it's pointing right at my face, and lets the slide fall forward. He watches the whole thing and just smiles, beaming with pride about his new gun toting girl friend.
I am so stunned and dumbfounded about the whole thing, I just stood there without saying anything. Next shot, she does it again. At this point I lay my gun down and step back from the firing line. I watched her empty the entire clip, each time tilting the gun to her right so it would have been pointing right at my head. I wait until she's done shooting (didn't want to spook the brand new shooter who's holding a loaded weapon) and then tell her what she's doing. She seems embarrassed and apologizes.
I'm thinking she's new and it was a simple mistake. I walk back up and proceed to shoot. After her boyfriend shows her how to load it back up, she tilts the gun to the right, again pointing it right at my head, and slides another round back in. At this point I'm glaring at both her and her boyfriend and and let them know that she did it again. Her boyfriend gives me a look like I'm ruining this first experience for his girlfriend. Idiots. I waited until they left before continuing to shoot.