What's the software you use the most on your computer? Be it desktop or laptop. For me, it'd be Pages, the MacOS's default typing software.
Slack, Mail (the default OS X Mail app), iTerm 2, Safari, Sublime Text and iA Writer.
Google Chrome & LibreOffice
I guess... the browser... and the antivirus (because it always runs in the background). Other than those, I use photo and video editing software, such as Photoshop and AVS Video Editor.
I tend to use Google Chrome all the time, I also use Photoshop, Skype, FileZilla and Gyazo.