I personally hate widdly fretwanking guitar solos so I'm going to nominate the guitar solo from Bone Machine by the Pixies. We could all learn something from Joey Santiago's technique:

1. Play one chord over and over.
2. Keep playing the same chord when the main riff comes back in so you get loads of lovely dissonant harmonies.
3. Slowly slide down the fretboard, making a jolly untuneful racket on the way down.

What do you have? The greatest guitar solo EVER.