If you're looking for a really tasty chocolate bar without sugar, give the CarboRite chocolate truffle bar! It's got milk chocolate with think truffle layers built in!
This isn't a "huge" candy bar - it's 1oz and just a bit bigger than a credit card. But it only has 1g of effective carbs and believe me, it can be VERY satisfying because it is so rich. It's not just milk chocolate - it has chocolate truffle spots within in that is perfect for savoring.
It's sweetened with Splenda, too, so there isn't any aftertaste at all. Just the rich, creamy chocolate flavor.
If your local shop doesn't carry this bar yet, be sure to ask them to bring it on in!
UPDATE: Carbolite/Carborite have now adopted the more PC / all-diet friendly company name of "Health Smart Foods".
Low Carb Chocolates and Candies