-Jellyfin (i was astonished that this piece of software wasn’t mentioned before)
-SMPlayer (imho the best front end for MPV)
-shutdown command (i use it daily)
-Lutris
-Wine
-Piper (to manage keybings on the mouse with a gui) (is also the only one that I found that works with my G502, if you have an alternative please tell me, i want to check it out)
-ckb-next (for managing leds and keybindings for my keyboard)
-openRGB
Honorable mention:
Molly (the FOSS version, a privacy focused client for Signal)
Edit:
Almost forgot about QEMU+kvm for virtualization
Mumble (is comoletely free software and has a better quality even than teamspeak)