Back in the 1980's Will Sergeant of Echo & the Bunnymen used to attach paperclips to his guitar strings. In his own words ,he would "twat it one" Thus producing the desired distortion effect.
In my early days messing around with stuff I tried winding loose strings in a figure of 8 type loop between the strings right up beside the bridge.. Try it out it makes wierd noise, might be what your looking for.
I was also attaching small objects at the higher harmonic points of the string near the bridge ( about 2 -5 cm up the string ) enough to be fixed but loose enough to rattle.
Also.. Two strings nearly tuned to each other produces a pulsing effect.. You could look into that.