Try this on for size and let me know what y'all think: I have a comic book from the mid-'80s in which the main character is pursued through the jungle by enemy soldiers. He stops long enough to bury shotgun shells just below the surface, with the primers down and resting against a nail. The running soldiers step on the shells, the primers are struck...BOOM. I have my doubts on this one too...seems that the nail would need something to somehow keep it hard against the primer. But assuming that it did somehow get set off, what do you think the effects on the hapless victim's foot would be? Like the BB gun thing, with no barrel to travel down, would it drastically reduce the velocity [and thus the tissue damage] of the shot load?
Seen on a bumper sticker: "Exercise. Eat right. Take vitamins. Die anyway."