I've been using Burp Intruder (part of Burp suite), but in the free edition of Burp Suite the Intruder functionality is Time-throttled. As a student pen tester however, I can't justify the cost of $300 a year for the Burp Suite Professional Edition.
I know there are other great intercepting proxies out there (OWASP ZAP), but I'm after something specifically that simulates the burp intruder core functionality, mainly the login validation checks via either 'pitchfork' methods.
It doesn't need to be integrated as part of a intercepting proxy suite, a standalone tool is fine also. It must be free or very low cost.