Here's an unusual one, not so much a super-nasty defense load, but a quiet deer-poaching trick:
Take your kid's break-action .410 single shot and one .410 shell (standard or magnum), pry open the shell crimp and pour out the shot charge. Leave the shotcup or wad in place, along with the powder charge.
Next, get an aluminum hunting arrow, the kind with flexible rubber fletching. Stick the arrow's nock into the .410 case. Carefully roll the "feathers" against the arrow shaft and cram the entire arrow and shell into the breech. The tip of the arrow should clear the muzzle by a few inches, even squeezing through the full choke that is common in single-shot scatterguns. You complete it by screwing the hunting broadhead in place.
When fired, the arrow springs from the muzzle with a muted *POP*, since there is less compression on the powder charge. As the arrow clears the muzzle, those rubber fins pop right back out, stabilizing the arrow. With practice, it is a very effective way of harvesting deer that lurk out there beyond bow range. Typically, the arrow goes clean through.