Here is an open position fingering for the major pentatonic scale in open G tuning. This scale is commonly used by players like Ry Cooder and Mark Knopfler along with many Nashville guitarists.
Next is a Country guitar part using the G major pentatonic scale. It features lots of hammer-ons and pull-offs. Notice how easy it is using the open strings to play Country rhythm guitar with this tuning. As with every scale, experiment with the major pentatonic to create your own riffs, licks and solos in open G tuning.