If you're going to eat ice cream, then damn the health concerns: Head to Marble Slab, which never disappoints. Pimply teenagers scoop the thick, rich ice cream onto a marble countertop, where the customer has a choice of ingredients to have mixed in. The hands-on process is slow but worth it. Lines of enthusiasts can stretch out onto the hot sidewalk--teenagers, stoners, and elderly couples brought together by their love of ice cream. Once you get there, try the coconut-banana flavor. This combination, fairly common in Mexico, is impossible to find anywhere else except this Southwestern chain. What makes it so special is the way the fruit flavors lighten the heavy texture of the high-butterfat ice cream. In other words, it's just the right amount of a good thing.