Like Patriot, my reason was squirrel interdiction, but for defending bird feeders rather than garden plants. At first we tried all the environmentalist-approved ways of keeping the bushytails away from the feeders: strategic location, baffles, etc. Some could penetrate even the most clever countermeasures, though. So, we even resorted to giving the squirrels their own food supply, which they consumed with gusto ... along WITH the birdfood, the greedy little creeps.
So, in a non-PC moment, we resorted to buying a ... ohmygosh ... a GUN! Now we have a feeder perimeter such that if you come into it, you'd best be sportin' feathers. We do have a measured response, though. Tree rats sniffing around on the ground get a spanking from my wife's Beeman GH500. If they actually get onto the feeders, they buy a Crow Magnum from a Winchester 1000 above the diaphragm. After that, they don't come back ... some voluntarily, most not.
In the meantime, I've learned that there's a lot more to air rifle technology than just what you can get at your friendly neighborhood hardware store. I've also gained a greater appreciation of firearms and shooting sports in general.