The Amarillo burger is my personal favorite.
As others have said, don't be in a hurry. It'll take a half hour or so to get your food, and that's assuming they aren't crowded. I like to go early so I can get in and out of there before the devil worship crowd arrives. Plus, I just can't deal much with Sixth Street anymore.
The cook can be surly but that's part of the charm. We dubbed him the Burger Nazi. They have a nice patio in the back where you can eat without having to look at all the Satanic stuff on the walls.
imho, it's gone downhill a bit lately. Still damned good but not near-orgasm good like it was 4-5 years ago.
If you're ever in San Antonio, Chris Madrid's kicks the crap out of Camino and anybody who says otherwise hasn't been to Chris Madrid's.