Bugzilla. It is one of the older and more adopted development tools with issue tracking capabilities. It is used by well-known Open Source projects such as GNOME, KDE and Linux kernel itself. It features many advanced options, like a search system with a comprehensive reporting tool, capable of generating charts and automated scheduled reports. Like Redmine, it is extensible and customizable, and is able to create custom workflows for bugs. It also supports a wide range of databases and programming languages.
Trac. This tool integrates bug tracking capabilities with its wiki and the revision control system chosen by the user. It incorporates project management capabilities, a customizable reporting system, timelines, support for multiple repositories, built-in spam filtering, and is available in many languages. There are plugins available to adapt the tool to your needs.
Do you know any other issue tracking tool? We encourage you to share it in the comments below!