Just use a pitch shifter, vocal processors are great and all...just no need to spend extra cash if you have some guitar/bass/keyboard related effects that can do the job.

If you don't have any that can, might want to check out the Yamaha Magic Stomp...while it doesn't completely replace an analog chain of effects. Its a great jack of all trades that can do exotic things other stand alone units and many multi units couldn't hope to do.