WPMU DEV - WPMU offers WordPress Plugins, WordPress Themes, WordPress Multisite and BuddyPress Plugins and Themes.
strace - Trace system calls and signals. A diagnostic, debugging and instructional userspace utility.
MAMP - MAMP is the abbreviation for Macintosh, Apache, MySQL, and PHP. It is a reliable application with its four components that allows you to access the local PHP server as well as the database server (SQL).
ftrace - A function tracer for the Linux kernel.
Firefox Developer Edition - Built for those who build the Web. The only browser made for developers.
Valgrind - Valgrind is an instrumentation framework for building dynamic analysis tools.