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.

Watch the demo video:

Download Sound Chopper