Ask HN: Cool keyboard shortcuts you use that have made your life easier?

I'm curious about shortcuts you've found or created that have made your life easier (you don't have to be a programmer).

For instance, ever since I found out about Vimium and CVim, I can't think of a better way to browse the web using keyboard (what the heck was I doing all those years before that?!)

Another example: I've set up many customized keyboard shortcuts (some use macros) in Word that have made a significant difference on my productivity and how much I enjoy typing in the software.