There are a few excellent analog octave / pitch shifting pedals out there. It’s certainly harder to engineer good ones but the payoff is big, since you can avoid all the ad > da conversion artifacts that rear their ugly heads once you start recording.

I’m surprised nobody here mentioned the Microsynth…

https://www.ehx.com/products/micro-synthesizer

… however these are great too …

http://www.godlyke.com/totally-wycked-audio-effects-pedals/great-divide (custom order)

http://www.foxroxelectronics.com/Octron2.html