It seems like every region of the United States has their own version of a BBQ sauce. Some are sweet, some are tangy, some have a lot of tomato and others are more mustard based. Some BBQ sauces are red, others brown and some are even yellow or white! Talk to different people and you will likely get different answers regarding which kind of BBQ sauce best.
Head to the Carolinas, particularly to the regions around both Lexington and Piedmont, and you will find a BBQ sauce very different than the sweet tomato kind from Kansas City or the smokey sauce from Texas. Carolina Red Sauce is a thin vinegar based sauce that is very tangy and served as a mop sauce and finishing sauce for pulled pork. It is even great as a mop sauce for smoked ribs. Mop some on before you add a finishing BBQ sauce.