Shotgun!! You sissy! What you need is a MG42, Prairie Dogs don't stand a chance, its like shooting Prairie Dogs........ in a prairie.
The largest overkill I have ever seen though was just outside of Fallujah some of the boys from the 1st Marine Division, 1st Tank Battalion noticed a dog (some ugly flea ridden mix bread) running up to them with a satchel strapped to its back, a main gun round from a M1A1 Abrams 120 mm smooth-bore cannon doesn't even leave blood behind.