I like a 9mm for that purpose. I carry one each trip to the woods--the same gun I carry everywhere else. If hunting, you probably have a more substantial caliber for your main gun, but the 9mm can always be there, ready for the unexpected rabbit or bad guy.
I have to say that the a 9mm pistol is my all time favorite gun for general use, be it Ruger, Beretta, Glock or whatever. Sight it in with your choice of defense loads (the curren best being Hornady Critical Duty), and then see where the hardball rounds print so you can pot that occassional small critter.
For more specific use, I carry something else, like a heavy caliber revolver for deer, but always, the 9mm is there.