A so called "attack proxy", Snark
allows a user to monitor and edit HTTP requests and responses.
Snark can be configured to act as a web proxy, or in a tunnel mode
which allows for proxy chaining, or use with other tools. Snark
was written in perl and should run in any environment that is supported
by perl, and wxWindows.
source (old) --
win32 installer (new) --
discussion group