The Phrygian and Locrian have particularly exotic sounds, although as you advance as a guitarist, you'll realize that you can make any scale sound exotic, it's just the notes that you are playing. This is the idea of "modes"; there are tons of pages regarding modes on this website, it'd be worthless to explain it again, etc.

The way i play exotic types of sounds now...I add chromatics. Usually, if i'm playing in a major key, i'll add the bIII from the parallel minor, and flat the major seventh...then I add some chromatics every once in a while; Nothing is concrete, though; most scales are. That's the trick, is never be concrete in your playing. Just because the D note isn't in the E major scale doesn't mean you can't play it. Play it! it's called E dorian, if you follow the guidelines of D Major, inverted.

Always change! play the 3rds, 5ths, unisons, etc, there are no rules, and basically what i mean is that eventually you'll find yourself playing out of feeling, and not out of scales.

Sorry for the rant, i haven't done that in a while. :D