My favorite gun for small critters is my 10/22 take down model with a set of Tech Sights on it. Shoots nice and accurate, eats any ammo (loves CCI) and splits in half for easy packing. The nice thing about the 10/22 over other .22 pack rifles is it takes maybe 10 secs to put together or take apart and doesn't wear out over time. For bigger varmints I grab Dad's .22WMR Henry which is great but the Ruger is my favorite of the two.
*Edit* Forgot to include I got a very nice fox with it a little while back. Only pics are on my crappy cell phone so I can't share