I use the usual ruger 10/22 with a 10 power scope,
nothing better in my opinion for getting them but i usually hunt ground squirrls so i think they are harder to get close to then real squirrls thus a scope is the key for me
Here is a pic of my ground squirrl success along with genesis 27:3
PS. I know a lot of you have seen this pic but i still love it!