Mac - Erase hard drive completely.

Mac - Erase hard drive completely.
I want to sell or give away my old Mac but want to completely wipe off the hard drive so that even the pros can't read it.

I have "Shred" for my PC, any utilities for the Mac?

Wipe and shred a half-a-dozen to a dozen times or so and you should be very safe. If you're really worried about pros recovering data then you should destroy the HD physically. When I say pros, I mean organizations with a backroll for that type of thing. If you're worried about typically computer geeks then 2 or 3 times is probably sufficient, maybe even once.