Boss RPS-10 Digital Pitch Shifter / Delay Micro Half Rack - $300

Crazy mono delay - you should definitely watch some Youtube videos.
The unique feature is the "Keyboard Control" input, which lets you to use a second audio source to modulate the frequency of the pitch shift effect applied to the main input.
That pitch tracking is a lot less accurate / reliable than something like MIDI, which can lead to some interesting unpredicted results.
It does have a somewhat high noise floor, from my experience.
YMMV based on your power setup