You're gonna want to use FX-13 for its 13 classic effects and 24 possible presets! Quickly select effect, change effects settings, and jump to presets.
Record a sample and instantly get 24 variations of it! One 'clean' version and 23 'mutated' versions: one for each key! Resample your mutations to build up new ones! Endless!
EnvelopeFX is a multi-effect patch that uses incoming audio's volume envelope to control effects! Automate the effect and its parameters!
Punchy HRando FX
You could almost call this one a randomizer's randomizer, but... Punch in a transposable sequence that controls a sampler that randomly picks one of four possible samples to play per key.