For squirrels, wood chucks, crows, foxes, skunks, badgers, and other things I won't publically admit shooting...
http://www.airgundepot.com/gamo-whisper.html?green=14305023661This will certainly take down much bigger animals, but other guns are better suited if you have wild pigs or coyotes causing problems. It'll do the job, but a .22 is better in those cases.
For small game and pest control, I prefer Air rifles. Not a cheap wall-mart bb gun, but a high powered air rifle, between 1000-1500 ft/second. The "Whisper" pictured above is what I use. It is quiet, which is a benefit for me, since I use it for pest control in the anti-gun commie mecca of NY. They rate it at 1200 FPS, in practice it's more like 1000FPS, but always round down whatever number is advertised. I'm not the best shot in the world, but it's accurate enough that I can head-shot squirrels at about 100 yards, so there's still some meat left on them when you're done. For things like woodchucks, and foxes, it's good for leaving the pelt undamaged, as opposed to a .22 that leave a pretty big exit hole sometimes, this is no bigger than a pencil point, hard to see under the fur.