Spring modulator
The same as an envelope follower, except adjusting the 'bounce' adjusts the lowpass's resonance. Use this to process a control signal so that rapid changes oscillate back and forth, like pushing a pendulum that swings at shorter intervals until coming to a rest.
Slug clicks
Great for random modulation. Inspired by Soulacybin's "Dangatang", which itself was inspired by Dr. Steve Brule. For your health.
Doom Sine
Sine wave with Amplitude modulation on white noise, same concept as the one mick gordon used in Doom 2016.
Metallizer
Uses an allpass node feedback loop to get a kind of metalic sound out of whatever you run through it.