1) Nuclear - Desktop music player focused on streaming from free sources (in beta phase):
https://github.com/nukeop/nuclear
Nuclear Mastodon account: @nuclear
2) Pidgin - IM with options to add various third party plugins which enables you to use facebook chat, steam chat, etc, XMPP included.
https://bitbucket.org/pidgin/main/src
3) Synchting - cross platform peer to peer file synchronization, also available on f-droid:
https://github.com/syncthing/syncthing
As an alternative to Pidgin -- Psi+ (it has a better support for OpenPGP)
And I forgot another one! 😀