RandARP is a free VST plugin arpeggiator with many randomization features, allowing incoming notes or chords to be manipulated in various rhythmic ways.
Sure, VCV Rack is not new and the second post here. But since constantly new versions and modules are being created, here´s a little reminder 😉
Btw, the latest improvent is an unofficial VST patch for fx and instrument use. Installation is a bit of a hassle at the moment though. Support in the KVR forum (Link at the bottom).
This might be the craziest library for Native Instruments Kontakt that you can find. It´s from Embertone and it´s free.