I'm not the biggest fan of risers, but if you really need them, with pitch automation and various oscillators, least one of them being some sort of noise. Plus crazy LFO effects, turn on your "random mode" and mess around with everything. That implying you're using a synth. I have done some interesting stuff with ableton's frequency shifter and random audio samples, it totally destroys the harmonics and sounds very dissonant but could be interesting in some situation. Add a little reverb or some stereo separation tools and you should be good to go.