Shiner is a nice "mainstream" beer. It amazes me how much it has spread outside of Texas in the last few years.
I like a lot of the local brews I have tried in the Austin area. 512 Brewery and Live Oak Brewery both have great lineups. I don't care for the 512 Wit, but everything else I have tried has been great. From 512 my favorites are the Pecan Porter and the Pale; Live Oak I prefer the Primus, but it's Winter seasonal only.
There is also Southern Star Brewery out of Conroe, TX. They are fairly new I believe, but the "Bombshell Blonde" is one of the better beers I've tried in the past year.
As others have mentioned, St. Arnold's has a good lineup too. I like the Fancy Lawnmower.