Alleyoop is a graphical front-end to the increasingly popular Valgrind memory checker for x86 GNU/ Linux using the Gtk+ widget set and other GNOME libraries for the X-Windows environment.
Bokken is a GUI for the Pyew project. It provides an interface to almost all the features of Pyew.
D-Feet is a D-Bus debugger that allow you to view names on the session and system bus, view exported objects, interfaces, methods and signals, view the full command line of services on the bus, and execute methods with parameters on the bus and see their return values.
GTestRunner is a GTK+-based graphical frontend for running unit tests in Perl. It offers several improvements to the underlying unit testing framework that make test-driven development in Perl even more comfortable.
GtkInspector is the built-in interactive debugging support in GTK+. It was added in GTK+ 3.14, based on a copy of the well-estabished gtkparasite.
KMD is a graphical debugger. It can debug hardware over serial ports such as the Manchester ARM Board or with software emulators (ARM and MIPS emulators are included in the project).
Zephyr is an automated functional and regression testing tool. It will test any application, written in any language, that has a GUI interface. Zephyr takes the place of a user: Pointing, clicking and entering text.