Re: ONE GUN
My choice will probably be a lot different from most here.
I'd probably opt for a fast, flat shooting 22 centerfire. Such as a 22-250 or maybe a 223 WSSM.
Great accuracy, plenty of good bullet selections, and not as rough on meat and fur.
Being limited to only one rifle, puts my mind in a self sufficient survival mode. ( IE. I screwed up and did something really stupid and was faced with either disappearing, or spending the rest of my life in a cage ) I would be limited to only what I could carry. Luxuries are out, a single rifle would have to provide both food and fur. Big holes make for cold blankets.
If I can kill that coyote from here, Will you walk out to get him?