https://www.cnet.com/news/one-of-youtubes-best-paid-features-is-now-free-for-android-oreo-phones/

Okay, maybe it's not the best feature. Perhaps you'd rather have something else. 

But I think it's pretty nifty that, starting today, I can keep watching a YouTube video in the corner of my screen while doing other things on my phone. I hit play on a video, press the Home button, and keep watching while I surf and browse.