After watching most videos from 2019 WWDC I went back to the previous years' keynote and tried to make the same list of 'best videos' to watch.
These first three are a must every year. Some year the keynote is on a lower tone than another, but overall that's what we came for. Same thing for the state of the union.
The Design Award is not a must, but it is interesting to watch just to take a note at what Apple considers to be the apps that are there to set a trend for the year or that they're using some new SDK features in a neat way.
As for above, these 3 are good to at least skim through to see the most important changes in the frameworks that we use on a daily basis. You might add other sessions on other Apple frameworks you use a lot, like for example Core Data,…
Introducing Dark Mode
This is obviously just for macOS since dark mode for iOS only came in 2019 with iOS 13.
Let me know if I missed some great sessions (I probably did).