I was surprised to find that a simple gzip -9 produced a significantly smaller file (29539 bytes). Since jQuery is pretty much a textbook example of "compress once, decompress a gazillion times", I started to play around with various DEFLATE encoders. My intention was to spend tons of CPU cycles while compressing in order to save every byte possible.
Google's Zopfli, especially Krzymod's fork, produces the best results, which can be found here:
http://minime.stephan-brumme.com/jquery/2.1.4/. kzip and 7zip are included in my tests as well.
Moreover, I downloaded these libraries from their original websites and from major public content delivery networks like Google, Microsoft, cdnJS, jsdelivr, Yandex and Boot. With a few exceptions they all fail to be even comparable to gzip -9. I have no idea why because smaller files would directly lead to reduced network costs.