Among the tools I am experienced with, these stand out.
I work extensively with JavaScript and jQuery, using these "unobtrusive" technologies to enable site owners to track and understand user behavior on their web sites. So much of what you see in your browser is the result of analysts (like myself) demonstrating and quantifying what activities and options are being used by visitors. Although you can't track something that doesn't happen (you can't report on which pages were viewed zero times, for example), you can use your vision of what does happen to expand those opportunities that are working. This usually pushes out what doesn't work.
Once the data is collected, it has to be turned into reports that bring out the nature of the activity on the site. As an analyst, I show what is happening, and explain how this benefits or hinders business goals. An important part of the analytical role is steering business owners away from "nice to have" data questions; usually, I do this with the simple question, "What's the business case for that report?" (Of course, sometimes, the business case is, "My boss asked me for it.") Our focus is (should be) on data collection that enables us to make sound business decisions about improving site performance.