Ditto. My paternal grandfather had a chunk of German mortar round in his skull. It may well have saved his life, since it occurred just days before the Battle of the Bulge. He was busy recuperating at a rear-area hospital while the rest of his armored division were in the thick of it.
Oh, and for a WTF injury -- my father-in-law is a big man. Probably 300lbs+. Several years ago, he was on a ladder working on the roof of their lakehouse when the ladder slipped. He wound up falling more or less straight down and landing on his ass. At first, he was completely unable to move his legs. He managed to pull himself inside, wake his wife, and they drove him to the hospital. By the time he got there, he had gotten the feeling and movement back in his legs, and he just had really bad back pains. They did some X-rays and didn't see anything. No broken bones, no internal tissue damage, etc. So they gave him some painkillers for his back and sent him home.
By the time they got home, there was a message on the answering machine from the hospital telling him to come back
immediately. Turns out somebody had the idea to *count* his vertebrae. There was one
missing.
Best guess is that the way he landed (basically in a sitting position) put all the force of impact in a straight line through his spinal column, and one of the vertebrae basically
disintegrated. That pain he was having was because two of the discs were just smushed together and all the nerves there were going "AAAAAHHHH WTF theres supposed to be a bone here". They never found the vertebrae. Not even chunks of it. It was so finely pulverized that it just dissolved into the surrounding tissue. If he had been leaning forward or backwards just a few degrees either way when he hit, his spinal cord could have been pinched or even severed. As it was, it was so straight when he hit that the vertebrae just restacked around it.
They had to do massive surgery and put a substantial amount of metal in his back. As I understand it, his case is in several advanced medical textbooks now.