Texas produces two popular dark-coloured 'bock'1 beers: Shiner Bock and Ziegen Bock. Shiner Bock is an actual Texas beer from a Texas brewing company, the Shiner Brewing Company of Shiner, Texas (Shiner is located between Dallas and about one hour's drive north of Austin). Ziegen Bock is its Anheiser-Busch competitor, and is proudly served only in Texas, but tastes suspiciously like the Michelob Amber Bock which is sold outside Texas.
In large cities in Texas, these beers are almost as widely available as Budweiser (brewed by Anheiser-Busch) or Miller Lite, the two leaders outside Texas. In short, almost every place in Texas sells this stuff, often on draft, so you can afford to be selective about where you drink it. In cheap places, it goes for US$1.50 per twelve-ounce serving. If you pay more than that for it, you'd better be consciously paying for the atmosphere.
These beers should not be mistaken for German bock beers, which are much stronger. Texas Bock beers are relatively light-bodied, though not light-coloured. The combination of light body and flavour makes these beers somewhat like an English bitter, only watered down and served ice cold. Given how beastly hot Texas often is, if you find yourself there, Texas Bock beers can be a pleasant drinking experience.