This Union Market counter—and its newer, bigger Wharf sibling—shucks just three kinds of oysters, all Chesapeake and all cultivated by the outfit that owns the restaurants. Still, the three varieties couldn’t taste more different, from creamy Rappahannocks to aggressively briny Olde Salts. We always start with a dozen (and throw in some fresh clams), then grab a snack or two—peel-and-eat shrimp, baked clams with Thai sausage and coconut, or cobia crudo with smoked avocado. At the Wharf, there’s a really good diner-style cheeseburger, and both places serve the fabulous fried-oyster po’ boy. Moderate.