Using Harmonic Minor Scales is a simple way to add exotic sounds to your guitar playing! By using the Harmonic Minor scale you can build interesting ii-V-i patterns, or more accurately iim7b5 - V7 - im7 patterns. The raised 7th in the Harmonic Minor Scale creates a major 3rd in the V chord, effectively changing the vm7 in a minor scale to a Dominant 7th chord in the Harmonic Minor Scale. The examples below are in the key of E Harmonic Minor, and use the B7 arpeggio to build tension, as the D# in the B7 wants to resolve to the Root "E".
E Harmonic Minor ii-V-i: #1
E Harmonic Minor ii-V-i: #2
E Harmonic Minor ii-V-i: #3