We used to sneer at those amateurs who insisted on making this tequila-and-lime confection take a pass through the blender. The best margaritas, we'd insist, are always on the rocks. Then we were introduced to the Sixth Street Margarita at the cavernous, comfortably dim Tempe franchise of this laid-back chain. Okay, so they're talking about the Sixth Street in Austin, not Tempe, but we don't care. Z'Tejas started in Texas, but is now headquartered in Scottsdale, and in any case, there's no topping the ice-smooth agave taste and the wallop that leaves us no choice but to call a cab. And once we've decided not to drive, well, why not have another? Oh, hey, and make ours the one spiked with Chambord.