I've used KoGrid before, but I was never happy with the syntax for writing templates. You have to define your HTML as strings inside your Javascript. Yuck.
Magnific Popup is a great little jQuery plugin that creates responsive lightbox's for images. I've used a few lightboxes, but this one definitely has the fewest number of issues when moving between desktop and mobile sizes.
Modern browsers support the history.pushState api for changing the URL without actually navigating on the page. This is a nice replacement for hash-based navigation (where a hash-route is used to change the page without navigating, due to the hash not going to the server) since the URL looks like a normal, clean url. Other than smoother navigation, the implementation is invisible to the user.
Unit Testing in javascript is usually pretty straightforward. You pick a framework like Jasmine or QUnit, you write some tests, and you run them in your browser or in something headless like PhantomJS.
Durandal is currently my Javascript MV* framework of choice. It's flexible, powerful, and written by the same guys who did the WPF MVVM framework Caliburn.Micro.