I've looked all over the web, and I cant find anything that tells how to get the chainsaw, and I know its real because of this: http://www.youtube.com/watch?v=xpYoefQ_2Bo0:23 seconds into the video is where hes using it, I've been told its in a different version or something, but if you have it, or know how to get it, please speak up.
I think they said they would have it out in a patch later. I read the dev blog once and they said something like that. Chainsawww!