the most recommondations would be a bit expensive.
I like for sounddesign:
Befaco Oneiroi: as looper, fx processor - combines delay, resonator, delay and more
Befaco Noise Plethora - digital noise source with analog filters
Bastl Dark Matter for industrial feedback and rhyrmically modulation
Mimeophon for delayed Feedback and Karplus Strong
Make Noise Spectraphon to alter spectral character of sounds
Qu-Bit Aurora Spectral Reverb - adds a special spectral effect
Schlappi Angle Grinder - as filter, waveshaper or vco
Benjolin V2 - as multimode filter filter and sound design tool
Rabbit Hole Apollow View - for Tube Saturation / -distortion
schlappi BTFLD
Plasma drive - erica synths / game changer audio
Koszalin Xaoc Devices
OpticShifter Teia
SMEAR Smoothie Audio
Greetings
Chris