To my taste, the only pickles that are good are the ones that my family always called "new" pickles--the ones that are still a fairly bright green, by virtue of having been pickled for only a brief period of time. In that genre, the best (if you can get them) are definitely Guss's, from the Lower East Side of Manhattan. If you don't have access to them, the Batampte brand (in jars, always refrigerated) that is sold in some supermarkets is a decent substitute.
The typical type of pickle, to my way of thinking, has been "embalmed" for a very long period of time, and winds up being limp and dull in appearance. The "new" pickles, by comparison, are always crunchy and very fresh in taste.
To return to the subject of kosher pickles, or just kosher food in general, I want to reiterate something that renfrew (?) said, by way of correcting someone else. When you see the "kosher" designation on a packaged food product, this does NOT mean that it has been blessed by a Rabbi. Instead, it means that the entire production facility has been inspected for cleanliness, and that the production process has been continually supervised to be sure that the cleanliness is maintained. That normally includes disassembling the machinery at fairly frequent intervals, and cleansing them with live steam.
This designation also means that no "unkosher" items have come into contact with either the food or the processing machinery. This latter part is not necessarily important for those who do not keep a kosher home, but the absolute cleanliness that is required for the certification should interest everyone.