I can't really pin down one best, but among the best shows I've ever seen was ZZ Top at FEC in April 1982. This was their first show in Austin since the infamous Foot Stompin' Barndance and BBQ at Memorial Stadium 8 years earlier. There was an energy around campus that I had never before felt for a show, and I've never felt it since, and the show itself did not disappoint.
A couple other memorable shows were Johnny Winter at the Austin Opera House in September 1981. Stevie Ray Vaughan opened for him, and Tommy Shannon (formerly with Johnny Winter) had just joined Stevie's band. It was general admission, and I was able to elbow my way to the front of the stage, so I got to watch both Johnny and Stevie doing their thing from literally an arm's length away.
Also saw Johnny Winter at the Texas Opry House in Houston in November 1978. The perfect venue for him, and I was luckily able to sneak in, as I was still under-age. I was only 17 at the time, and since the place served alcohol, you were supposed to be over 18 to get in. Fortunately, my provisional driver's license had a full face picture, instead of the usual profile, so I was able to sneak past the doorman. Anyway, about 3/4 of the way into the show, Johnny starts taking requests from the audience, so he played a lot of his older stuff. Great, great show. i miss that man.