Sound Chopper is an application built in Max/MSP and for Mac OS X by sound designer Matteo Cerquone. It allows you to manipulate and transform pre-recorded sound through its many sound effects such as pitch shifter, reverb, delay and looper etc. The downside is that it's a stand-alone, not a plug-in which means you'll have to record the sound in Sound Chopper and then import it into your DAW of choice. Considering that you get great sound design possibilites for free, it seems like small enough downside.
Sound Chopper – Free Standalone App for Mac
About the Author: Madeleine Bloom
Madeleine Bloom is a musician, producer, multi-instrumentalist and singer from Berlin. She studied Electroacoustic Music at the Franz Liszt Conservatory. In the last few years she's worked as a technical support for Ableton and has helped countless people with her in-depth knowledge of Ableton Live, various other music apps as well as audio engineering.