I have never killed a deer with one, but I have shot quite a few 410 slugs. My old single shot shoots them very accurately. It would be my first choice, but I sure wouldn't hesitate to shoot a deer with them (close range of course).

I have killed several deer and hogs with buckshot out of a 12 ga, and it is very effective. I wouldn't even consider it out of a 410. You probably wouldn't get more than a couple of pellets.