When I am hunting big game I take any shot that I can take in my judgment that has close to a 100% chance of success. My best situation is always a standing broadside shot when I have something to rest the gun on but in reality that situation isn't always present. While I have never attempted a head shot because I view that as low probability of success, I have used a neck or high shoulder shot when the yardage was right and that was all there would be for an opportunity. When still hunting or tracking deer which is the way I like to hunt a standing shot is what we all strive for but often you are faced with a running deer and just a few seconds to evaluate whether it is something you want to kill and if you can make a killing shot. As for the ethics vs legal debate I see a divide between the two. One is a personal benchmark and the other is a legal line in the sand.