Jimi Hendrix performing Purple Haze, even when he is spaced out, he can still play the guitar effortlessly.
Eric Clapton performing Layla.
In 1969, Clapton fell in love with Pattie Boyd, the wife of one of his best friends, Beatles' George Harrison. At about the same time, one of Clapton's friends gave him a copy of "The Story of Layla and Majnun" as written by Azerbaijani poet Nizami. The book moved Clapton profoundly as it was the tale of a young man who fell hopelessly in love with a beautiful, unavailable woman and who went crazy because he couldn't marry her. Clapton saw the correlation with his own life. more here.
The Who headed by Pete Townsend performing "Who are you"
"Who are you", is now recognized as the theme for the popular CSI series. "Who are you" is a rock classic, Pete Townsend managed to slip in "Who the f*ck" are you" which passed the censors when it was performed on American TV for the first time.
Slash previously in Guns and Roses, performing the Godfather theme on electric guitar.
Slash dropped a note in the 1992 Argentina performance but the crowd loved it anyway.
Last but not least, Lynyrd Skynyrd with Free Bird.
You might have heard this song in Forrest Gump.