No GDB in the new Command Line Tools (OS X Mountain Lion) for Xcode - September 2013? I've recently formatted my Mac and when I reinstalled the command line tools, I installed the new  Command Line Tools (OS X Mountain Lion) for Xcode - September 2013. I've just typed gdb in my terminal to debug one of my programs and it told me -bash: gdb: command not found. There is no gdb in these new command line tools, is there?

If it doesn't, where can I get it? How can I install it?

Is brew install gdb one choice?
Apple switched to clang/lldb some times ago.

You can still install gdb from brew with brew install gdb as suggested. You'll probably want to install gcc with it (you'll have to specify the exact version of gcc you want, eg. brew install gcc47).

Some privileges are needed for gdb to work and you'll need to code sign the binary. See instructions given by brew.