Watching Terry Kath shred his guitar playing 25 or 6 to 4 on this video posted on ConcertVault is absolutely jaw dropping:
http://www.concertvault.com/chicago/video/25-or-6-to-4_1942162436.html
I think he set the bar so high it hasn't been topped yet 45 years later. If you know of a performance by any rock artist that can even approach this please post a link.
