A few, all of which fall into the category of "luck" versus "skill".
I have an occasional problems with pidgeons getting into my barn. They're messy, nasty things that crap all over the place. So, of course I shoot them when I can. The problem is, when you walk into the barn, and turn on the lights, they start flying around, and usually fly out the holes in the walls (its an old barn) pretty quick. So you have a very limited window to make the shot. Last time, I saw a couple fly into the barn so I grabbed my (scoped) .22, stuck a magazine in it at headed for the barn. Walked in the door, saw pidgeon on the other side of the barn, up high, threw the gun up (like you would a shotgun, no attempt at using the scope, and its semi-dark, even during the day), and pulled the trigger. Pidgeon dropped outa the rafters like a stone. I had center-punched him right through the chest!
Going back a few years: My first gun (age 14) was a single shot, bolt action .22. Living in a semi-rural area, we used to hunt woodchucks year round. Of course being young and stupid, I didn't have any idea that you probably shouldn't be taking 200 yard shots with a .22. And I actually killed a few 'chucks at 150-175 yards or so. Of course I missed about 40-50 times for every one I actually hit. So (having read WAY too much Jack O'Conner), I saved my pennies, and bought a .270 (Model 70, lightweight, SHORT barrel, withe 3-9x scope) when I was just shy of 15.
So we're out in the field one day, and see a woodchuck W-A-Y out there, in the downhill corner of a big field we were hunting. just visible to the naked eye. Since we were in grass about 3 feet high, I had my buddy sit up and I rested the rifle on his shoulder. I had no real idea of the range, except it was much longer than than the 100 yards I'd sighted the rifle at. So I held at least a foot-and-a-half high, and let fly. Pretty much cut the 'chuck in half. We paced it out to something like 375 paces.
P.S. My buddy never quite forgave me for that one...Said his ears rang for about a week after...I imagine he's got permanent hearing damage (as I do), from that shot.