Playing over the blues one can have a lot of choices besides just the pentatonic scale. To sound' jazzy' a common device used is to use a melodic minor up a 5th.e.g over G7th you can use D melodic minor.This enables you to take your blues vocabulary into different territory and explore a new space. It's definitely one of those sounds you have heard and liked but are not able to figure what 'it' was. The spelling of a melodic minor scale is 1,2,b3,4,5,6,7. So it's a major scale with just the 3rd flattened.:)
Here is a ready reckoner for common scales in use.It will be nice to take each one and plot them to pilfer chords. I do this to any new sounds. Chords in addition to really cool string skip shapes.
https://docs.google.com/open?id=0B5qJqMU7g1nHX2c1RUM1RE9oUFk