I have seen a few deer killed with a .410 slug.
A guy here in town actually killed a 230lb 11pt with one last year. One shot too. Now thats a big deer for SC and a big deer anywhere to be taken down with a .410.

I even asked him why he was hunting with it b/c I know he has more rifles better suited and he replied, "I just wanted to try it on a doe, I didn't know the biggest buck of my life would walk out.".