DDD is a graphical front-end for command-line debuggers such as GDB,
DBX, WDB, Ladebug, JDB, XDB, the Perl debugger, the bash debugger,
or the Python debugger. DDD displays data structures as graphs and plots.
I like DDD because it provides an easy-to-use interface to GDB. I could debug my code even without knowing anything about GDB. Actually, I learnt how to use GDB thanks to DDD, through its excellent in-program documentation. I use DDD to hunt for the usual segmentation fault, and it is excellent at it. It also has many more advanced functions, such the graphical display of arrays using gnuplot. The biggest shortcoming in my opinion is the lack of syntax highlighting of the source code. To install it on a Mac it's actually very simple: just use Macports or Homebrew. An early reviewer clearly ignored this, and gave 1 star based on this ignorance.