Here’s a short list of applications I use on my Linux workstations and servers.
Gnu Image Manipulation Program is a great editor for a variety of raster image formats.
VLC is a great player for a huge number of audio and video formats as well as UPnP/DLNA network streaming. The Windows version has some bugs with network stuff but it works great on Linux. I personally don’t like it as a music player but it is my default video player.
I have been running MariaDB (a fork of MySQL) for quite some time now but I still use this to muck around with the databases. It gives a warning when connecting but I haven’t noticed any major compatibility issues.
Screen is simple program that you should invoke immediately every time you connect to a remote machine over SSH. If your connection dies, your running task will not be terminated and you can reconnect to it afterward. It also does a whole bunch of other cool things but that’s the main one.