Since it hasn't been mentioned yet, NoScript imo. Some sites run an absolutely absurd amount of scripts and the majority are not required for the site to function. So at best, there's no value from letting them run.
I could maybe see selectively-blacklisting particularly obnoxious websites
That's what uBlock Origin already kinda does for you. It's not just an adblocker, it also blocks tracking JavaScript from various sites as well as a bunch of other crap.
Mmmm....okay, but the parent comment I was responding to does have a point in that there are some benefits to blocking Javascript above and beyond just trying to deal with tracking. Like, if you're on a laptop, there are sites that will burn a lot of CPU time -- and hence battery life -- doing nothing useful. Or, on an older machine, it can speed up page loading.
My issue is just that unless you're going to turn it on yourself on a site-by-site basis, killing off Javascript breaks too much of the Web today. It was a viable option to just have on back when there was a meaningful portion of the world that didn't have Javascript available and web developers designed pages to deal reasonably with its absence and you were willing to deal with flipping it off on specific sites to deal with the occasional breakage...but today, it's a huge portion of the Web that doesn't work without Javascript.
No don't get me wrong. uBO doesn't block all JavaScript. It has lists with individual scripts that are known to be used for ads or tracking, and these get blocked. All the other scripts load as usual. This already improves website load times and probably also battery life. Another interesting solution for reducing CPU load may be DNS based blocking. That way, the CPU is not impacted at all, the browser tries to load the script but it just silently fails, because the DNS records for the tracking and advertisement servers won't be provided.