Survival gun?

If I were planning on surviving in the wilderness, hunting for small game as food, it would be a simple break-open single-shot .22LR rifle.

If I were planning on surviving in a close quarters urban area with human adversaries coming after me, it would be an AK47 7.62x39 rifle with a .35+ caliber large capacity semi-auto handgun as backup.

If I were planning on surviving from a defensible position where I could pick off incoming bad guys from a distance, just about any .30 caliber hunting rifle with a scope would do.