GDB for interactive debugging is a useful tool in the embedded developer's tool chest. It is a stable, well-documented and well-known entity. It has the ability to debug remotely by placing an agent on the target, be it gdbserver for applications or kgdb for kernel code and, although the default command-line user interface takes a while to get used to, there are many alternative front-ends. The three I mentioned were TUI, DDD, and Eclipse, which should cover most situations, but there are other front-ends around that you can try.
A second and equally important way to approach debugging is to collect crash reports and analyze them offline. In this category, I have looked at application core dumps and kernel oops messages.
However, this is only one way of identifying flaws in programs. In the next chapter, I will talk about profiling and tracing as ways of analyzing and optimizing programs.