After looking at other's lists I think I am missing a good document server. Emby isn't the best music and photo server so I could look at improving that, but it has been good enough for those purposes that I haven't felt like going to the trouble of installing anything else.
Aster: Multiseat software for Windows allows several users to work on the same PC.
LaunchBox: Frontend for DOSBox, modern PC games and emulated console platforms.
I bought both Plex and Emby. I started with Plex but had some technical issues related to my machine having multiple IP addresses so I switched to Emby. I tried Jellyfin before switching to Emby but it wasn't as capable as Plex or Emby (at least at the time) and I wanted something with some commercial support behind it. I have been pretty satisfied with Emby, but do wish it would get requested features added in a much more timely manner.