Nothing as exciting as elk or bighorn sheep, but I've had it happen. Duck hunting. Loaded up my gear, and put two rounds in the tube of my 870. It was before shooting hours and I figured that would be a little safer wading out to the blind, thigh-deep in water, in the dark, than fully loading the gun (one in the chamber). I got to the blind, had a cup of coffee, and waited for shooting hours. The ducks came in, cupped and started to land in the hole. I popped up, shouldered the gun, and nothing. I'd forgotten to chamber a round. I got a gorgeous view of the ducks flaring away into the sunrise, I guess.