I tend to use the whole tone scale (C D E Gb Ab Bb C) a bit too much. The cool thing about the scale is that lots of harmonies work. You can use a major 3rd (C to E), minor 6th (C to Ab), and minor 7th (C to Bb). All will produce a different "sound". If you want to get dissonant and nasty, harmonize a major 2nd (C to D), or a diminished 5th (C to Gb).
Ron