I picked up a CZ Ringneck in 16 gauge a couple years ago to round out my shotgun collection and always wanted a side-by-side. Got a few grouse with it that fall. Not a real fancy gun, but for the money is a nice side-by-side unit.
My father had a single shot HR in 16, and that was the first shotgun I ever shot, so always had a sweet spot for it.
The shells aren't as common, but if you don't shoot a lot of clay pigeons with it, you'll be able to find hunting loads without too much trouble at most gun stores.