Why I use NotScripts: the extension lets you enable JS temporarily or permanently for a particular website with just a mouse click. As well, at the same time, you can do the same thing for any third-party JS because it presents you with a list of them. So you can enable jsquery and disable google-tracker at the same time.

It's much easier than navigating the menu system to add an exception to the list of blocked sites for each time you just want to read a PDF, for example. That's the main use-case for me.