When my sister the chef used to visit New Orleans, the first thing she'd do after checking into a hotel was head for a convenience store and buy a couple of bags of Zapp's potato chips. After all, a trip to New Orleans is a culinary expedition, Zapp's are top-drawer chips, and the Crescent City was the only place you could get 'em. A bag of Zapp's and some olive salad from Decatur Grocery were typical take-home souvenirs of a trip to New Orleans. Now the chips are in Dallas, available first at Eatzi's and now at Tom Thumb. In addition to all their regular flavors like Cajun Crawtaters--hot 'n' spicy, blackening-seasoned, crisp, potato-tasting chips--Zapp's also puts out feature flavors, special seasonings available for a short time only. Imagine--limited-edition potato chips. Of course, there's really still only one place to get good olive salad.