Wouldn't it depend on what you intend to shoot with it?
A cheap 12 gauge shotgun.
-A 12 gauge can take down any man or beast in North America.
-They are effective out to 100 yards (further than most people will need a self-defense/utility firearm)
-They are cheap and reliable (you can find used 870's or 500's for $200 or less).
-For up-close civilian self-defense situations their effectiveness can't be matched.
Why would you want a single shot? I'd want as many rounds as I could have available without having to reload.
Stoeger side-by-side. With buckshot, much easier to point and click.