We are huge fans of Mantis (www.mantisbt.org). It strikes me as lightweight compared to many solutions advertised here, and has the virtue of being agnostic be

We are huge fans of Mantis (www.mantisbt.org). It strikes me as lightweight compared to many solutions advertised here, and has the virtue of being agnostic between PostgreSQL and MySQL. It's also completely free. We integrated it extensively with Subversion a few years ago, and there already exist pre-built Git integration modules for it. The plugin ecosystem has come a long way. One important criteria to me personally was the suitability of it for use as a project management and/or feature roadmapping system, not just an actual _bug_ tracker per se, explicitly for bugs in the sense of defects. Mantis performs extremely well on this count as well. Probably the biggest high-profile use of Mantis I know is Digium's issue tracker for Asterisk: http://issues.asterisk.org/ http://issues.asterisk.org/ -- you can see it in action there. Their particular use of it relies on Mantis's extensive ACL features (optional--you don't have to get that complicated if you don't want to!) to open the process of enrollment and bug submission to the public at large, to allow certain people intermediate levels of access (e.g. QA testers), and to impose an actual hierarchy of developers, managers and bug marshals inside the company.