One of my favorite stouts is Oesterstout by the Schelde Brewery.
The website states:
During the brewing process, the wort of the beer is pumped across the oyster shells.
Is this what gives it it's distinct taste? In Denmark, another more easily available Oyster stout is Marston's Oyster Stout. Do all Oyster Stouts follow this particular process, or is it more of a sales pitch?