Have you ever used a shock collar?

I have never used a shock collar and I never would. I think that it's horribly cruel and unethical. I can imagine anyone who uses such methods being a good person. Like commenters before me, I think that it's unnecessary and wrong to inflict any kind of pain on your pet. Dogs are friendly by nature and as long as you treat them good they will be cooperative (unless they were traumatized in the past, of course). Some people just have unrealistic expectations from they dogs, they want them to act against their nature but won't even spare the time to teach them.