GNU DeBugger. An interactive debugging utility.
Graphical user interfaces to gdb:
AMG 2008-04-16 PYK 2012-12-15: The latest release of Insight (6.8-1, posted 2009-07-19), embeds Tcl/Tk 8.4.1 and [incr Tcl] 3.2. I imagine it could benefit greatly from a newer version of Tcl. For example, libgui/src/subcommand.c is obsoleted by namespace ensembles, libgui/library/list.tcl contains an implementation of lassign, and libgui/library/lframe.tcl provides a labelframe.