Website Grader - Grade your website's strengths and weaknesses in seconds.
strace - Trace system calls and signals. A diagnostic, debugging and instructional userspace utility.
Checkbot - Checkbot will boost the SEO, speed and security of your site by checking you're following 50+ web best practices. Browser extension with free and paid plans.
ftrace - A function tracer for the Linux kernel.
PageSpeed Ninja - One-click page speed boost for WordPress
perf - Perf is a simple app monitoring solution paired with meaningful alerts.