GL, and Hal Jordan specifically, pretty much starts and ends with the legendary Gil Kane. There is an energy and dynamism in his work that is rearely matched. Kane of course kicked off the Silver Age with his run on Green Lantern that stands as a monumental tenure to this day.
Working/learning from Kane's art, as sampled here, what amazes me is the simplicity he employed but was able to retain so much energy. I encourage fellow artists to pick up one of the DC Showcase collections and learn a thing or two!