Hardanger is an open source web application penetration testing platform for Microsoft Windows operating systems.
Current Features

Native Windows feel via Windows Presentation Foundation
Can run as a Fiddler2 add-on or standalone
ClickOnce installer with automatic updates (standalone version)
Context tab allowing inspection of full HTTP requests
Server fuzzer tab to configure and launch the server fuzzer
Basic random fuzzer generates random strings of UTF8 characters of random lengths
Non HTTP 200 detection engine
Results window keeping track of successful detections
Ability to review requests/responses in the results details window

Download
http://hardanger.codeplex.com/releases/view/81426