Joe needs to be a little more specific. If you need a quick meal birdshot will put food on the table as long as you're close enough to bag a bird or a small animal. You'll need slugs or heavy buck shot at closer range than slugs to bag a few days worth of meat from one large animal.
As for 2 legged predators you definitely have to be up close and personal for bird shot to be effective and still within pretty close proximity for heavy shot to save you against homo-sapien predators. Slugs will work well. A double barrel needs to be physically reloaded very fast if you're outnumbered. If you're up against those 'assault weapons' with a double barrel you're screwed.