Simple alternative to larger solutions like Bugzilla, CBT allows Mac OS X developers to track bugs, features and enhancement requests for their projects, using their favorite UI: Cocoa.
No more slow and, more or less, ugly, web-based user interface: you use a native Cocoa application to access your database on local or wide-area network.

Add any kind of attachements (pdf, jpg, tiff, text, movies, ...) to your entries
Manage users and groups
Notify other developers by e-mail
Real-time notification of modifications: connected users see updates in real-time
Generate reports using XML, XSLT and FOP

See screenshots

CocaoBugTracker is available as
Free Standalone, for individuals (1 database, 1 project, 1 user, no source code)
Registered Standalone, for individuals, (1 database, Unlimited projects, 1 user, no source code)
Network, for small groups, (Unlimited databases on local network, Unlimited projects, Unlimited users, no source code)
Network Pro, for groups, (Unlimited databasess on local and wide-area network, Unlimited projects, Unlimited users, source code)
More info