I've seen two instances with 12ga slugs, both accidental, one resulting in an instant kill, the other in a wounded animal.
My father, in his younger years, was the best natural shooter I have ever seen. We were walking up a trail near deer camp when a large doe broke out of the edge of the woods on a dead run. My dad unshouldered his gun and shot before I even reacted. Two deer went head over heals. He shot the doe through the shoulder and her doe fawn on the other side through the head. We never saw the fawn until it was dead.
The other time, I had a small heard of doe and fawns in front of me. I thought I was being careful to not take a shot that might hit two deer. The intended target dropped where she stood and the rest ran away. When I went over I could immediately see a blood trail leading away (being snow on the ground). When followed it an jumped the deer about 100 yards away but she promptly went to posted land we can not enter. Obviously, we never found her. I still can not fathom how I could have hit that second deer.
I've seen videos of 2-1 shots with compounds bows, crossbows and rifles. I can foresee certain situations where I might be confident of a "2-fer" but I'd say the odds of that shot materializing that I would be comfortable taking are about like the Powerball Lottery odds.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.