Or phone, or after an OS reinstall, etc. Just got to thinking about it because I did a fresh install of Arch on my chromebook the other day, and I'd be curious what other people's priority software installs are. For me, after the basics like drivers, it's xfce, Firefox, Transmission, Libreoffice, and VLC on linux. Pretty much the same on Windows, plus a few utilities like 7zip, PuTTY, and notepad++. For Android installs I grab nova launcher, Hangouts Dialer, F-Droid, NewPipe and MoonReader before anything else.
EDIT: Forgot firefox on android, as well as ublock origin on all platforms.