Firefox+uBlock (web browser)
MEncoder (video encoder)
OBS (screen recording and streaming software)
Inkscape (vector illustration software)
Mumble (VoIP chat room server/client/protocol)
Julia (programming language great for scripting and mathematics)
For Unix systems:
Wezterm (terminal multiplexor)
i3 (window manager)
Over a decade ago when I was big into gaming it was the best option over competition like Ventrilo and TeamSpeak. Still have a server to this day even though many gamers seem to have moved onto talking over Discord voice calls or channels.