Watch the In and Out online guitar lesson by Jeff McErlain from 50 Eclectic Blues Licks You MUST Know
Here is a cool lick to be used over a dominant 7th chord. It is a mixture of a minor and a major blues scale. The formula for this scale is R,2,b3,3,4,b5,5,6,b7. It can also be seen as a mixolydian scale with an added b3 and b5.
This sound is pretty common in the blues and jazz and a scale you should really get comfortable using! From Eric Clapton to Mike Stern, this sound is a must.