OWASP ZAP

OWASP ZAP (short for Zed Attack Proxy) is an open-source web application security scanner.
It is intended to be used by both those new to application security as well as professional penetration testers.
It is one of the most active Open Web Application Security Project (OWASP) projects and has been given Flagship status.
When used as a proxy server it allows the user to manipulate all of the traffic that passes through it, including traffic using https.
It can also run in a daemon mode which is then controlled via a REST API.
ZAP was added to the ThoughtWorks Technology Radar in May 30 2015 in the Trial ring.
ZAP was originally forked from Paros, another pentesting proxy. Simon Bennetts, the project lead, stated in 2014 that only 20% of ZAP's source code was still from Paros.
Features.
Some of the built in features include:
Intercepting proxy server,
Traditional and AJAX Web crawlers,
Automated scanner,
Passive scanner,
Forced browsing,
Fuzzer,
WebSocket support,
Scripting languages, and
Plug-n-Hack support.
It has a plugin-based architecture and an online ‘marketplace’ which allows new or updated features to be added. 
The GUI control panel is easy to use.