As far as free you could build a chain of effects intended for glitching. I recommend trying Destroy FX Buffer Override and/or Scrubby as well as Bram's Supatrigga.
Regarding the pay route I only really know of Sugarbytes Effectrix as being the only Mac compatible glitch plug. I'm sure there are more though...
Don't forget you can get cool glitchy effects by using standard DAW features too such as short delay times with a lot of feedback, timestretching, slicing, etc. A lot of work but you will more than likely be happy with your results!