I saw tons of great shows at SXSW (some of which I'll probably write on later), but I want to mention two that took me completely by surprise:
Guitar Wolf was a surprise guest the night of the Spoon/John Cale show. I was only there on a rumor that it would be the Arcade Fire, but GW put on a show far better than I could have expected. It was all half-ironic/half-serious rock'n'roll posturing, including floor-rolling, stack-jumping, spitting, drinking, windmills, shouting, and far greater volume than anything else that week. The highlight: when GW dragged an audience member up on stage to play, who also began rolling on the floor and jumping around. Absolutely fantastic, and now I'm going to end up searching out the albums that won't be half as good.
The second surprise: Los Super Seven. I went to see them at a party because I was intrigued, not so much because I had great hopes. They had recorded with some impressive people (including Caetano Veloso) and would be joined by Calexico, so I thought it would at least be good for some free food and decent entertainment. They went way beyond that level, though. Charlie Sexton sat in for most of the show, and I think he had as much fun -- and was as impressive -- as anyone. I haven't seen a band this large that was this tight in a long time, and even packed into a backroom on a hard bench, I loved every minute of it.