22lr been feeding me small game decades. I prefer bolt action, single shot or magazine fed doesn't matter to me.

Now you asked calibers and many replied with "gauges" and that's a passion! Mostly I use now, 20ga SxS. I have a single barrel blackpowder 28ga shotgun I am VERY fond of too. 3# 11 oz loaded! Takes any small game with authority, a BP shotgun is a shotgun you can custom load in the field And it's not completely off topic either cause 28ga is aka .54 cal and can fire a round ball too. Here's a pic of my baby.