The 22 LR is actually pretty suprising, I've seen it take out wild cattle, wild donkeys and horses. A friend of mine even took an elk (illegally) with one at a mountain they use to haul wood from, shot right behind the ear. One wild donkey I shot 4 times pretty quickly into the heart at about 30 yards or so, the bullets all penetrated and the heart was a pulp, just a cavity with blood when we butchered it (an uncle of mines makes jerky out of it, don't ask

) It also penetrated through a rib where one broadside shot I took went through (there are several youtube vids of people shooting through layers of wood and clothing with a 22). Most of the kills I've had have been with a 22 by far. It is cheap, easy to find, easy to be accurate with (no enormous blast to cause flinching) and rapid fire with a dot sight, you don't even lose the sight picture. I took out a coyote 2 months ago with one at close range, the bullet went through the vitals and he hemorrhaged out of his mouth trying to run away in a matter of seconds. Big bore, high velocity, full powered rounds all have their place, but I also believe in the saying "it is not the equipment but the operator." With the 22, and the way I have set my own up, it can put round after round into a 10 inch diameter at 50 yds no sweat without losing sight picture, a constant stream of accurate fire, with practically no recoil, double taps are possible at out to 60 - 70 yards (since I'm about stealth, I would try to shoot only out to a 150 yards and only if spotted), depends how much you practice. And you can carry over a thousand rounds no problem. The 10/22 I got is interchangeable with other 10/22 in case anything breaks down, and that is why I don't mind having one, of course I've shot a 22 from day one, so I might be a little biased. That said, here are some other folks who more to say.
http://www.survivalmonkey.com/forum/firearms/9361-lethality-22-lr-standard-velocity-round.html#post75834