Since you’re a guitarist and I assume you have a pedal or two laying around
This is a Keys only tip:
If you have a pedal of some kind you can create a feedback loop running from one of the tracks with one oscillator on the input from the pedal and the other on whatever whatever wave you want. Set the filter to tracking as well and you can use the AMP page to shape the feedback.
Pretty crazy sounds that are not much like the standard fare you get.
Also read this :
http://www.elektron-users.com/index.php?option=com_fireboard&Itemid=28&func=view&catid=9&id=213870#213870
It’s a little advanced but it’s very useful