I often use this exercise as a quick left-hand warmup. It's great for loosening up your left hand, especially for more complicated chordal work. It's also an excellent study for left-hand coordination and control. The concept is to play chromatic octaves starting on the low open E string entirely in first position. We will move up chromatically starting on the low E up to the G# on the first fret of the third string.
As I was walking around, I heard a violinist playing these wild exercises-he was wailing! I thought it would be really cool to adapt those licks to the guitar. Since the violinist didn't speak any English, I had to gesture for him to show me what he was doing. He gladly did, and then he showed me a bunch of variations, too. It was great; though we didn't speak, we nonetheless communicated very easily.