I think the simplest solution is probably the cat that was mentioned, or else a wiener dog. The reason their bodies are shaped that way was because they where bread to chase animals such as foxes and badgers out of their den.
There is no reason why a BB
gun shouldn't be able to take out a gopher, especially if you have a good CO2 cartridge in it.
As far as using a real weapon. I don't see any reason to go up to a centerfire cartridges such as the .223 or the .220 Swift, unless you are planning to take up varmint hunting, and shooting at a great distance becomes an issue. Some of those guys will burn up 10 grand on a rifle, handloading components and Optics. But they are also able to get kill shots on gophers at 500 yards.
22 Long Rifle is a good small round, the shells are small and cheap and their are numerous pistols and rifles around, so you should be able to find one that fits your lifestyle. Some of the .22LR rifles out there will also take the quieter and smaller ranged .22 Short. Not as common a shell as it was in yesterday it won't rattle the neighbors quite as bad.
Also you might consider the .17 Hornaday. This was a new rimfire round that came out a couple of years ago. It shoots very straight and puts out all around better numbers then the .22LR. Very little drop in the shell in flight. AFAIK Ruger and Marlin, who developed the round in conjunction with Hornaday are the only ones making rifles for it. I can't wait for Ruger to configure a 10/22 with that shell. Should be a winner.
You may also consider the .22 WMR. This is another rimfire rifle that hits harder then the common 22LR. The tradeoff is expense and a larger shell. I have a Single Six revolver that will shoot either .22WMR or .22LR depending on which cylinder is installed.
That is my Ptarmigan gun when out walking.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.