Ive spent my fair share of time in the "butts" and like others have said, its definitely something I wont soon forget.
You also occasionally hear a round fall short and hit the dirt if the shooter forgot to adjust his elevation settings when changing yard lines.
I did have an experience where another marine was shooting from about 20 yards behind me. We were on a fire and movement exercise and the team member in the lead was the only one that was supposed to shoot. Apparently Castillo couldn't wait his turn, that or just forgot and sent half a magazine over my head. I thanked him later for at least remembering not to shoot me.
"Be kind, be courteous, and have a plan to kill everybody you meet."