I have killed Squirrels and Mule Deer with my marlin 357 magnum.
Head shots on squirrels if you want to save money (some times its easier said than done)
Shot placement is everything! I would rather take a round of 50BMG to the foot than a 22short to the base of the skull.
all 25 of my guns are 45/70 govt, 357 mag, 22 or 12 ga... I believe in keeping it simple