There is also lldb, it's kind of a replacement for gdb.

This is a quote from the page:

Quote:In order to achieve our goals we decided to start with a fresh architecture that would support modern multi-threaded programs, handle debugging symbols in an efficient manner, use compiler based code knowledge and have plug-in support for functionality and extensions. Additionally we want the debugger capabilities to be available to other analysis tools, be they scripts or compiled programs, without requiring them to be GPL.