WebScarab
WebScarab is a web security application testing tool. It serves as a proxy that intercepts and allows people to alter web browser web requests and web server replies. WebScarab also may record traffic for further review.
WebScarab is an open source tool developed by The Open Web Application Security Project, and was implemented in Java so it could run across multiple operating systems. In 2013 official development of WebScarab slowed, and it appears that OWASP's Zed Attack Proxy Project is WebScarab's official successor, although ZAP itself was forked from the Paros Proxy, not WebScarab.