I went to use GDB in OS X v10.9 (Mavericks), and it's not there. Where has it gone?
# /usr/lib/gdb
-bash: /usr/bin/gdb: No such file or directory
# gdb
-bash: gdb: command not found
I also launched Xcode 5.0.1:
Preferences > Downloads
..and there's no longer command line tools available — ffs!