Winreducer.
I have reduced windows Iso over 1 gb. the final size is about 2.2 gb 2.4 gb depending if I install on desktop or laptop with wireless drivers.

I really think it's a great tool, it just takes some time to get it setup how you want it. I removed net framework and had to reinstall it with dism as I don't have steam on my laptop which would install it for you anyway :) .