A personal favorite of mine is the hungarian minor scale, and its family.
The scale formula is 1 2 b3 #4 5 b6 7. To me, it is like the harmonic minor with the augmented fourth from the lydian mode that adds quite a bit of symmetry and adds a challenge in performance. It adds a bit of fire to the more sad and mundane minor scale.
The A hungarian minor scale is spelled: A B C D# E F G# A.
Applying modal theory to this scale is also interesting, as some of the modes have many uses.
Ionian-type: 12-7-55-396 a.k.a. Major Augmented = #2 3 4 #5 6 7
Dorian-type: 12-7-55-96 = b2 bb3 4 b5 b6 bb7
Phrygian-type: 12-7-55-209 a.k.a. Byzantine a.k.a. Gypsy a.k.a. Double Harmonic = b2 3 4 5 b6 7
Lydian-type: 12-7-55-404 a.k.a. Unaugmented = #2 3 #4 5 #6 7
Mixolydian-type: 12-7-55-152 a.k.a. Undiminished = b2 b3 b4 5 b6 bb7
Aeolian-type: 12-7-55-310 a.k.a. Hungarian Minor = 2 b3 #4 5 b6 7
Locrian-type: 12-7-55-204 a.k.a. Oriental Major = b2 3 4 b5 6 b7
I marked the scale with root altered by the #4 with pink and the scale with root altered by the major 7 with blue, and the notes altered by modal permutations in red and blue, so that you can compare the resultant scales with the families of the major scale and harmonic minor scale.
Chord structures are:
i IIb5 III+ ivo (no 3) V VI vii
Cycling to the fifth as a new root, the chord structure is:
I II iii iv Vb5 VI+ viio (no 3)
Some songs that use the Hungarian minor scale are "Blue Honey" by Boštjan Zupančič and the theme song from the Nickelodeon TV show "Inspector Gadget"
The Khereb song "13 Rings" uses the Byzantine scale, which is from the same scale family.