So what is the most impressive guitar playing you ever witnessed in person?

For me, I would have to say seeing Allan Holdsworth live. His technique is min blowing. He is so advanced musically too. In fact, so advanced that I sometimes get bored of his playing... because he plays so many notes and the harmonic complexity is often beyond my understanding... in other words - I sometimes don't get it. I suspect I'm not alone there, but he sure is impressive and inspiring for me to listen to, in the right amounts.

I would have to mention John Scofield too. His improvisation skills are incredible. Seeing him live is incredibly inspiring, from the improvisation perspective.