Jeff Beck and Eric Clapton have performed together several times over the years. They've even toured together.
But in terms of pure entertainment value, I haven't found anything as enjoyable than the clip at the bottom of this story.
It's from the Secret Policeman's Other Ball, a benefit show that took place September 9, 1981, at the Drury Lane Theatre in London. The show was produced by John Cleese of Monty Python and was eventually released as a film and album.
Although Beck and Clapton performed several songs together that day, including "Crossroads," the one performance that has sort of taken on a life of its own—with its nearly 1.4 million plays on YouTube—is their hopping rendition of Bobby "Blue" Bland's "Farther Up the Road."
It finds them trading solos, Clapton on a Strat with his clean late-Seventies sound, Beck playing Seymour Duncan's Telecaster, starting out high on the neck, then launching into a Billy Gibbons-like pinch harmonic. While there's a great deal of tasteful stuff flying off the frets of both veteran players, Clapton's facial expression during Beck's solos sort of says it all.
His reaction is capped off at the 2:29 mark, when he lifts his arm as if to say, "Yeah, that was some pretty cool stuff, folks. I'm as impressed as you are."
Of course, there's more Beck after that; his next solo starts at 3:24. The band is rounded out by Mo Foster on bass and Simon Phillips on drums. Enjoy!