[ladberg]

I was about to call you out on ⌘-Down opening a file but I just tried it and was amazed that it works (most of us do ⌘-o or just double click).

Deleting a file is ⌘-Delete.

Everything in the Finder sidebar is removable (I've removed Recents and Tags, though I find Airdrop and iCloud Drive useful) and you can add custom stuff if you want something else (I always put my home folder at the top of the sidebar, it used to be there by default on earlier OSes).

⌘-Q is useful for closing apps, but I usually just open up the switcher (⌘-Tab) then while keeping ⌘ pressed you can tab over to other apps and just press Q to quit them.

[saagarjha]

⌘↓ mirrors ⌘↑ for going up a directory, except if you invoke it on a file the logical thing is to open it rather than navigate.